//===- SCCP.cpp - Sparse Conditional Constant Propagation -----------------===//
-//
+//
// The LLVM Compiler Infrastructure
//
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
-//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
//===----------------------------------------------------------------------===//
//
// This file implements sparse conditional constant propagation and merging:
// * Proves values to be constant, and replaces them with constants
// * Proves conditional branches to be unconditional
//
-// Notice that:
-// * This pass has a habit of making definitions be dead. It is a good idea
-// to to run a DCE pass sometime after running this pass.
-//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "sccp"
#include "llvm/DerivedTypes.h"
#include "llvm/Instructions.h"
#include "llvm/Pass.h"
-#include "llvm/Support/InstVisitor.h"
+#include "llvm/Analysis/ConstantFolding.h"
+#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Target/TargetData.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Support/Debug.h"
-#include "llvm/ADT/hash_map"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/InstVisitor.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/PointerIntPair.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include <algorithm>
-#include <set>
+#include <map>
using namespace llvm;
-// LatticeVal class - This class represents the different lattice values that an
-// instruction may occupy. It is a simple class with value semantics.
-//
-namespace {
+STATISTIC(NumInstRemoved, "Number of instructions removed");
+STATISTIC(NumDeadBlocks , "Number of basic blocks unreachable");
+
+STATISTIC(IPNumInstRemoved, "Number of instructions removed by IPSCCP");
+STATISTIC(IPNumArgsElimed ,"Number of arguments constant propagated by IPSCCP");
+STATISTIC(IPNumGlobalConst, "Number of globals found to be constant by IPSCCP");
+namespace {
+/// LatticeVal class - This class represents the different lattice values that
+/// an LLVM value may occupy. It is a simple class with value semantics.
+///
class LatticeVal {
- enum {
- undefined, // This instruction has no known value
- constant, // This instruction has a constant value
- overdefined // This instruction has an unknown value
- } LatticeValue; // The current lattice position
- Constant *ConstantVal; // If Constant value, the current value
-public:
- inline LatticeVal() : LatticeValue(undefined), ConstantVal(0) {}
+ enum LatticeValueTy {
+ /// undefined - This LLVM Value has no known value yet.
+ undefined,
+
+ /// constant - This LLVM Value has a specific constant value.
+ constant,
+
+ /// forcedconstant - This LLVM Value was thought to be undef until
+ /// ResolvedUndefsIn. This is treated just like 'constant', but if merged
+ /// with another (different) constant, it goes to overdefined, instead of
+ /// asserting.
+ forcedconstant,
+
+ /// overdefined - This instruction is not known to be constant, and we know
+ /// it has a value.
+ overdefined
+ };
- // markOverdefined - Return true if this is a new status to be in...
- inline bool markOverdefined() {
- if (LatticeValue != overdefined) {
- LatticeValue = overdefined;
- return true;
- }
- return false;
+ /// Val: This stores the current lattice value along with the Constant* for
+ /// the constant if this is a 'constant' or 'forcedconstant' value.
+ PointerIntPair<Constant *, 2, LatticeValueTy> Val;
+
+ LatticeValueTy getLatticeValue() const {
+ return Val.getInt();
+ }
+
+public:
+ LatticeVal() : Val(0, undefined) {}
+
+ bool isUndefined() const { return getLatticeValue() == undefined; }
+ bool isConstant() const {
+ return getLatticeValue() == constant || getLatticeValue() == forcedconstant;
+ }
+ bool isOverdefined() const { return getLatticeValue() == overdefined; }
+
+ Constant *getConstant() const {
+ assert(isConstant() && "Cannot get the constant of a non-constant!");
+ return Val.getPointer();
+ }
+
+ /// markOverdefined - Return true if this is a change in status.
+ bool markOverdefined() {
+ if (isOverdefined())
+ return false;
+
+ Val.setInt(overdefined);
+ return true;
}
- // markConstant - Return true if this is a new status for us...
- inline bool markConstant(Constant *V) {
- if (LatticeValue != constant) {
- LatticeValue = constant;
- ConstantVal = V;
- return true;
+ /// markConstant - Return true if this is a change in status.
+ bool markConstant(Constant *V) {
+ if (getLatticeValue() == constant) { // Constant but not forcedconstant.
+ assert(getConstant() == V && "Marking constant with different value");
+ return false;
+ }
+
+ if (isUndefined()) {
+ Val.setInt(constant);
+ assert(V && "Marking constant with NULL");
+ Val.setPointer(V);
} else {
- assert(ConstantVal == V && "Marking constant with different value");
+ assert(getLatticeValue() == forcedconstant &&
+ "Cannot move from overdefined to constant!");
+ // Stay at forcedconstant if the constant is the same.
+ if (V == getConstant()) return false;
+
+ // Otherwise, we go to overdefined. Assumptions made based on the
+ // forced value are possibly wrong. Assuming this is another constant
+ // could expose a contradiction.
+ Val.setInt(overdefined);
}
- return false;
+ return true;
}
- inline bool isUndefined() const { return LatticeValue == undefined; }
- inline bool isConstant() const { return LatticeValue == constant; }
- inline bool isOverdefined() const { return LatticeValue == overdefined; }
-
- inline Constant *getConstant() const {
- assert(isConstant() && "Cannot get the constant of a non-constant!");
- return ConstantVal;
+ /// getConstantInt - If this is a constant with a ConstantInt value, return it
+ /// otherwise return null.
+ ConstantInt *getConstantInt() const {
+ if (isConstant())
+ return dyn_cast<ConstantInt>(getConstant());
+ return 0;
+ }
+
+ void markForcedConstant(Constant *V) {
+ assert(isUndefined() && "Can't force a defined value!");
+ Val.setInt(forcedconstant);
+ Val.setPointer(V);
}
};
+} // end anonymous namespace.
-} // end anonymous namespace
+namespace {
//===----------------------------------------------------------------------===//
//
/// Constant Propagation.
///
class SCCPSolver : public InstVisitor<SCCPSolver> {
- std::set<BasicBlock*> BBExecutable;// The basic blocks that are executable
- hash_map<Value*, LatticeVal> ValueState; // The state each value is in...
+ const TargetData *TD;
+ SmallPtrSet<BasicBlock*, 8> BBExecutable;// The BBs that are executable.
+ DenseMap<Value*, LatticeVal> ValueState; // The state each value is in.
+ /// StructValueState - This maintains ValueState for values that have
+ /// StructType, for example for formal arguments, calls, insertelement, etc.
+ ///
+ DenseMap<std::pair<Value*, unsigned>, LatticeVal> StructValueState;
+
/// GlobalValue - If we are tracking any values for the contents of a global
/// variable, we keep a mapping from the constant accessor to the element of
/// the global, to the currently known value. If the value becomes
/// overdefined, it's entry is simply removed from this map.
- hash_map<GlobalVariable*, LatticeVal> TrackedGlobals;
+ DenseMap<GlobalVariable*, LatticeVal> TrackedGlobals;
- /// TrackedFunctionRetVals - If we are tracking arguments into and the return
+ /// TrackedRetVals - If we are tracking arguments into and the return
/// value out of a function, it will have an entry in this map, indicating
/// what the known return value for the function is.
- hash_map<Function*, LatticeVal> TrackedFunctionRetVals;
+ DenseMap<Function*, LatticeVal> TrackedRetVals;
- // The reason for two worklists is that overdefined is the lowest state
- // on the lattice, and moving things to overdefined as fast as possible
- // makes SCCP converge much faster.
- // By having a separate worklist, we accomplish this because everything
- // possibly overdefined will become overdefined at the soonest possible
- // point.
- std::vector<Value*> OverdefinedInstWorkList;
- std::vector<Value*> InstWorkList;
+ /// TrackedMultipleRetVals - Same as TrackedRetVals, but used for functions
+ /// that return multiple values.
+ DenseMap<std::pair<Function*, unsigned>, LatticeVal> TrackedMultipleRetVals;
+
+ /// MRVFunctionsTracked - Each function in TrackedMultipleRetVals is
+ /// represented here for efficient lookup.
+ SmallPtrSet<Function*, 16> MRVFunctionsTracked;
+
+ /// TrackingIncomingArguments - This is the set of functions for whose
+ /// arguments we make optimistic assumptions about and try to prove as
+ /// constants.
+ SmallPtrSet<Function*, 16> TrackingIncomingArguments;
+
+ /// The reason for two worklists is that overdefined is the lowest state
+ /// on the lattice, and moving things to overdefined as fast as possible
+ /// makes SCCP converge much faster.
+ ///
+ /// By having a separate worklist, we accomplish this because everything
+ /// possibly overdefined will become overdefined at the soonest possible
+ /// point.
+ SmallVector<Value*, 64> OverdefinedInstWorkList;
+ SmallVector<Value*, 64> InstWorkList;
- std::vector<BasicBlock*> BBWorkList; // The BasicBlock work list
+ SmallVector<BasicBlock*, 64> BBWorkList; // The BasicBlock work list
/// UsersOfOverdefinedPHIs - Keep track of any users of PHI nodes that are not
/// overdefined, despite the fact that the PHI node is overdefined.
/// KnownFeasibleEdges - Entries in this set are edges which have already had
/// PHI nodes retriggered.
- typedef std::pair<BasicBlock*,BasicBlock*> Edge;
- std::set<Edge> KnownFeasibleEdges;
+ typedef std::pair<BasicBlock*, BasicBlock*> Edge;
+ DenseSet<Edge> KnownFeasibleEdges;
public:
+ SCCPSolver(const TargetData *td) : TD(td) {}
/// MarkBlockExecutable - This method can be used by clients to mark all of
/// the blocks that are known to be intrinsically live in the processed unit.
- void MarkBlockExecutable(BasicBlock *BB) {
- DEBUG(std::cerr << "Marking Block Executable: " << BB->getName() << "\n");
- BBExecutable.insert(BB); // Basic block is executable!
+ ///
+ /// This returns true if the block was not considered live before.
+ bool MarkBlockExecutable(BasicBlock *BB) {
+ if (!BBExecutable.insert(BB)) return false;
+ DEBUG(dbgs() << "Marking Block Executable: " << BB->getName() << "\n");
BBWorkList.push_back(BB); // Add the block to the work list!
+ return true;
}
/// TrackValueOfGlobalVariable - Clients can use this method to
/// specified global variable if it can. This is only legal to call if
/// performing Interprocedural SCCP.
void TrackValueOfGlobalVariable(GlobalVariable *GV) {
- const Type *ElTy = GV->getType()->getElementType();
- if (ElTy->isFirstClassType()) {
+ // We only track the contents of scalar globals.
+ if (GV->getType()->getElementType()->isSingleValueType()) {
LatticeVal &IV = TrackedGlobals[GV];
if (!isa<UndefValue>(GV->getInitializer()))
IV.markConstant(GV->getInitializer());
/// and out of the specified function (which cannot have its address taken),
/// this method must be called.
void AddTrackedFunction(Function *F) {
- assert(F->hasInternalLinkage() && "Can only track internal functions!");
// Add an entry, F -> undef.
- TrackedFunctionRetVals[F];
+ if (const StructType *STy = dyn_cast<StructType>(F->getReturnType())) {
+ MRVFunctionsTracked.insert(F);
+ for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
+ TrackedMultipleRetVals.insert(std::make_pair(std::make_pair(F, i),
+ LatticeVal()));
+ } else
+ TrackedRetVals.insert(std::make_pair(F, LatticeVal()));
}
+ void AddArgumentTrackedFunction(Function *F) {
+ TrackingIncomingArguments.insert(F);
+ }
+
/// Solve - Solve for constants and executable blocks.
///
void Solve();
- /// ResolveBranchesIn - While solving the dataflow for a function, we assume
+ /// ResolvedUndefsIn - While solving the dataflow for a function, we assume
/// that branches on undef values cannot reach any of their successors.
/// However, this is not a safe assumption. After we solve dataflow, this
/// method should be use to handle this. If this returns true, the solver
/// should be rerun.
- bool ResolveBranchesIn(Function &F);
+ bool ResolvedUndefsIn(Function &F);
- /// getExecutableBlocks - Once we have solved for constants, return the set of
- /// blocks that is known to be executable.
- std::set<BasicBlock*> &getExecutableBlocks() {
- return BBExecutable;
+ bool isBlockExecutable(BasicBlock *BB) const {
+ return BBExecutable.count(BB);
}
- /// getValueMapping - Once we have solved for constants, return the mapping of
- /// LLVM values to LatticeVals.
- hash_map<Value*, LatticeVal> &getValueMapping() {
- return ValueState;
+ LatticeVal getLatticeValueFor(Value *V) const {
+ DenseMap<Value*, LatticeVal>::const_iterator I = ValueState.find(V);
+ assert(I != ValueState.end() && "V is not in valuemap!");
+ return I->second;
}
-
- /// getTrackedFunctionRetVals - Get the inferred return value map.
+
+ /*LatticeVal getStructLatticeValueFor(Value *V, unsigned i) const {
+ DenseMap<std::pair<Value*, unsigned>, LatticeVal>::const_iterator I =
+ StructValueState.find(std::make_pair(V, i));
+ assert(I != StructValueState.end() && "V is not in valuemap!");
+ return I->second;
+ }*/
+
+ /// getTrackedRetVals - Get the inferred return value map.
///
- const hash_map<Function*, LatticeVal> &getTrackedFunctionRetVals() {
- return TrackedFunctionRetVals;
+ const DenseMap<Function*, LatticeVal> &getTrackedRetVals() {
+ return TrackedRetVals;
}
/// getTrackedGlobals - Get and return the set of inferred initializers for
/// global variables.
- const hash_map<GlobalVariable*, LatticeVal> &getTrackedGlobals() {
+ const DenseMap<GlobalVariable*, LatticeVal> &getTrackedGlobals() {
return TrackedGlobals;
}
+ void markOverdefined(Value *V) {
+ assert(!V->getType()->isStructTy() && "Should use other method");
+ markOverdefined(ValueState[V], V);
+ }
+ /// markAnythingOverdefined - Mark the specified value overdefined. This
+ /// works with both scalars and structs.
+ void markAnythingOverdefined(Value *V) {
+ if (const StructType *STy = dyn_cast<StructType>(V->getType()))
+ for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
+ markOverdefined(getStructValueState(V, i), V);
+ else
+ markOverdefined(V);
+ }
+
private:
// markConstant - Make a value be marked as "constant". If the value
- // is not already a constant, add it to the instruction work list so that
+ // is not already a constant, add it to the instruction work list so that
// the users of the instruction are updated later.
//
- inline void markConstant(LatticeVal &IV, Value *V, Constant *C) {
- if (IV.markConstant(C)) {
- DEBUG(std::cerr << "markConstant: " << *C << ": " << *V);
+ void markConstant(LatticeVal &IV, Value *V, Constant *C) {
+ if (!IV.markConstant(C)) return;
+ DEBUG(dbgs() << "markConstant: " << *C << ": " << *V << '\n');
+ if (IV.isOverdefined())
+ OverdefinedInstWorkList.push_back(V);
+ else
InstWorkList.push_back(V);
- }
}
- inline void markConstant(Value *V, Constant *C) {
+
+ void markConstant(Value *V, Constant *C) {
+ assert(!V->getType()->isStructTy() && "Should use other method");
markConstant(ValueState[V], V, C);
}
- // markOverdefined - Make a value be marked as "overdefined". If the
- // value is not already overdefined, add it to the overdefined instruction
- // work list so that the users of the instruction are updated later.
-
- inline void markOverdefined(LatticeVal &IV, Value *V) {
- if (IV.markOverdefined()) {
- DEBUG(std::cerr << "markOverdefined: " << *V);
- // Only instructions go on the work list
+ void markForcedConstant(Value *V, Constant *C) {
+ assert(!V->getType()->isStructTy() && "Should use other method");
+ LatticeVal &IV = ValueState[V];
+ IV.markForcedConstant(C);
+ DEBUG(dbgs() << "markForcedConstant: " << *C << ": " << *V << '\n');
+ if (IV.isOverdefined())
OverdefinedInstWorkList.push_back(V);
- }
+ else
+ InstWorkList.push_back(V);
}
- inline void markOverdefined(Value *V) {
- markOverdefined(ValueState[V], V);
+
+
+ // markOverdefined - Make a value be marked as "overdefined". If the
+ // value is not already overdefined, add it to the overdefined instruction
+ // work list so that the users of the instruction are updated later.
+ void markOverdefined(LatticeVal &IV, Value *V) {
+ if (!IV.markOverdefined()) return;
+
+ DEBUG(dbgs() << "markOverdefined: ";
+ if (Function *F = dyn_cast<Function>(V))
+ dbgs() << "Function '" << F->getName() << "'\n";
+ else
+ dbgs() << *V << '\n');
+ // Only instructions go on the work list
+ OverdefinedInstWorkList.push_back(V);
}
- inline void mergeInValue(LatticeVal &IV, Value *V, LatticeVal &MergeWithV) {
+ void mergeInValue(LatticeVal &IV, Value *V, LatticeVal MergeWithV) {
if (IV.isOverdefined() || MergeWithV.isUndefined())
return; // Noop.
if (MergeWithV.isOverdefined())
else if (IV.getConstant() != MergeWithV.getConstant())
markOverdefined(IV, V);
}
+
+ void mergeInValue(Value *V, LatticeVal MergeWithV) {
+ assert(!V->getType()->isStructTy() && "Should use other method");
+ mergeInValue(ValueState[V], V, MergeWithV);
+ }
- // getValueState - Return the LatticeVal object that corresponds to the value.
- // This function is necessary because not all values should start out in the
- // underdefined state... Argument's should be overdefined, and
- // constants should be marked as constants. If a value is not known to be an
- // Instruction object, then use this accessor to get its value from the map.
- //
- inline LatticeVal &getValueState(Value *V) {
- hash_map<Value*, LatticeVal>::iterator I = ValueState.find(V);
- if (I != ValueState.end()) return I->second; // Common case, in the map
- if (Constant *CPV = dyn_cast<Constant>(V)) {
- if (isa<UndefValue>(V)) {
- // Nothing to do, remain undefined.
- } else {
- ValueState[CPV].markConstant(CPV); // Constants are constant
- }
+ /// getValueState - Return the LatticeVal object that corresponds to the
+ /// value. This function handles the case when the value hasn't been seen yet
+ /// by properly seeding constants etc.
+ LatticeVal &getValueState(Value *V) {
+ assert(!V->getType()->isStructTy() && "Should use getStructValueState");
+
+ std::pair<DenseMap<Value*, LatticeVal>::iterator, bool> I =
+ ValueState.insert(std::make_pair(V, LatticeVal()));
+ LatticeVal &LV = I.first->second;
+
+ if (!I.second)
+ return LV; // Common case, already in the map.
+
+ if (Constant *C = dyn_cast<Constant>(V)) {
+ // Undef values remain undefined.
+ if (!isa<UndefValue>(V))
+ LV.markConstant(C); // Constants are constant
}
- // All others are underdefined by default...
- return ValueState[V];
+
+ // All others are underdefined by default.
+ return LV;
}
- // markEdgeExecutable - Mark a basic block as executable, adding it to the BB
- // work list if it is not already executable...
- //
+ /// getStructValueState - Return the LatticeVal object that corresponds to the
+ /// value/field pair. This function handles the case when the value hasn't
+ /// been seen yet by properly seeding constants etc.
+ LatticeVal &getStructValueState(Value *V, unsigned i) {
+ assert(V->getType()->isStructTy() && "Should use getValueState");
+ assert(i < cast<StructType>(V->getType())->getNumElements() &&
+ "Invalid element #");
+
+ std::pair<DenseMap<std::pair<Value*, unsigned>, LatticeVal>::iterator,
+ bool> I = StructValueState.insert(
+ std::make_pair(std::make_pair(V, i), LatticeVal()));
+ LatticeVal &LV = I.first->second;
+
+ if (!I.second)
+ return LV; // Common case, already in the map.
+
+ if (Constant *C = dyn_cast<Constant>(V)) {
+ if (isa<UndefValue>(C))
+ ; // Undef values remain undefined.
+ else if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C))
+ LV.markConstant(CS->getOperand(i)); // Constants are constant.
+ else if (isa<ConstantAggregateZero>(C)) {
+ const Type *FieldTy = cast<StructType>(V->getType())->getElementType(i);
+ LV.markConstant(Constant::getNullValue(FieldTy));
+ } else
+ LV.markOverdefined(); // Unknown sort of constant.
+ }
+
+ // All others are underdefined by default.
+ return LV;
+ }
+
+
+ /// markEdgeExecutable - Mark a basic block as executable, adding it to the BB
+ /// work list if it is not already executable.
void markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest) {
if (!KnownFeasibleEdges.insert(Edge(Source, Dest)).second)
return; // This edge is already known to be executable!
- if (BBExecutable.count(Dest)) {
- DEBUG(std::cerr << "Marking Edge Executable: " << Source->getName()
- << " -> " << Dest->getName() << "\n");
-
- // The destination is already executable, but we just made an edge
+ if (!MarkBlockExecutable(Dest)) {
+ // If the destination is already executable, we just made an *edge*
// feasible that wasn't before. Revisit the PHI nodes in the block
// because they have potentially new operands.
- for (BasicBlock::iterator I = Dest->begin(); isa<PHINode>(I); ++I)
- visitPHINode(*cast<PHINode>(I));
+ DEBUG(dbgs() << "Marking Edge Executable: " << Source->getName()
+ << " -> " << Dest->getName() << "\n");
- } else {
- MarkBlockExecutable(Dest);
+ PHINode *PN;
+ for (BasicBlock::iterator I = Dest->begin();
+ (PN = dyn_cast<PHINode>(I)); ++I)
+ visitPHINode(*PN);
}
}
// getFeasibleSuccessors - Return a vector of booleans to indicate which
// successors are reachable from a given terminator instruction.
//
- void getFeasibleSuccessors(TerminatorInst &TI, std::vector<bool> &Succs);
+ void getFeasibleSuccessors(TerminatorInst &TI, SmallVector<bool, 16> &Succs);
// isEdgeFeasible - Return true if the control flow edge from the 'From' basic
- // block to the 'To' basic block is currently feasible...
+ // block to the 'To' basic block is currently feasible.
//
bool isEdgeFeasible(BasicBlock *From, BasicBlock *To);
// OperandChangedState - This method is invoked on all of the users of an
- // instruction that was just changed state somehow.... Based on this
+ // instruction that was just changed state somehow. Based on this
// information, we need to update the specified user of this instruction.
//
- void OperandChangedState(User *U) {
- // Only instructions use other variable values!
- Instruction &I = cast<Instruction>(*U);
- if (BBExecutable.count(I.getParent())) // Inst is executable?
- visit(I);
+ void OperandChangedState(Instruction *I) {
+ if (BBExecutable.count(I->getParent())) // Inst is executable?
+ visit(*I);
+ }
+
+ /// RemoveFromOverdefinedPHIs - If I has any entries in the
+ /// UsersOfOverdefinedPHIs map for PN, remove them now.
+ void RemoveFromOverdefinedPHIs(Instruction *I, PHINode *PN) {
+ if (UsersOfOverdefinedPHIs.empty()) return;
+ std::multimap<PHINode*, Instruction*>::iterator It, E;
+ tie(It, E) = UsersOfOverdefinedPHIs.equal_range(PN);
+ while (It != E) {
+ if (It->second == I)
+ UsersOfOverdefinedPHIs.erase(It++);
+ else
+ ++It;
+ }
+ }
+
+ /// InsertInOverdefinedPHIs - Insert an entry in the UsersOfOverdefinedPHIS
+ /// map for I and PN, but if one is there already, do not create another.
+ /// (Duplicate entries do not break anything directly, but can lead to
+ /// exponential growth of the table in rare cases.)
+ void InsertInOverdefinedPHIs(Instruction *I, PHINode *PN) {
+ std::multimap<PHINode*, Instruction*>::iterator J, E;
+ bool found = false;
+ tie(J, E) = UsersOfOverdefinedPHIs.equal_range(PN);
+ for (; J != E; ++J)
+ if (J->second == I) {
+ found = true;
+ break;
+ }
+ if (!found)
+ UsersOfOverdefinedPHIs.insert(std::make_pair(PN, I));
}
private:
friend class InstVisitor<SCCPSolver>;
- // visit implementations - Something changed in this instruction... Either an
+ // visit implementations - Something changed in this instruction. Either an
// operand made a transition, or the instruction is newly executable. Change
// the value type of I to reflect these changes if appropriate.
- //
void visitPHINode(PHINode &I);
// Terminators
void visitCastInst(CastInst &I);
void visitSelectInst(SelectInst &I);
void visitBinaryOperator(Instruction &I);
- void visitShiftInst(ShiftInst &I) { visitBinaryOperator(I); }
-
- // Instructions that cannot be folded away...
- void visitStoreInst (Instruction &I);
+ void visitCmpInst(CmpInst &I);
+ void visitExtractElementInst(ExtractElementInst &I);
+ void visitInsertElementInst(InsertElementInst &I);
+ void visitShuffleVectorInst(ShuffleVectorInst &I);
+ void visitExtractValueInst(ExtractValueInst &EVI);
+ void visitInsertValueInst(InsertValueInst &IVI);
+
+ // Instructions that cannot be folded away.
+ void visitStoreInst (StoreInst &I);
void visitLoadInst (LoadInst &I);
void visitGetElementPtrInst(GetElementPtrInst &I);
- void visitCallInst (CallInst &I) { visitCallSite(CallSite::get(&I)); }
+ void visitCallInst (CallInst &I) {
+ visitCallSite(&I);
+ }
void visitInvokeInst (InvokeInst &II) {
- visitCallSite(CallSite::get(&II));
+ visitCallSite(&II);
visitTerminatorInst(II);
}
void visitCallSite (CallSite CS);
void visitUnwindInst (TerminatorInst &I) { /*returns void*/ }
void visitUnreachableInst(TerminatorInst &I) { /*returns void*/ }
- void visitAllocationInst(Instruction &I) { markOverdefined(&I); }
- void visitVANextInst (Instruction &I) { markOverdefined(&I); }
- void visitVAArgInst (Instruction &I) { markOverdefined(&I); }
- void visitFreeInst (Instruction &I) { /*returns void*/ }
+ void visitAllocaInst (Instruction &I) { markOverdefined(&I); }
+ void visitVAArgInst (Instruction &I) { markAnythingOverdefined(&I); }
void visitInstruction(Instruction &I) {
- // If a new instruction is added to LLVM that we don't handle...
- std::cerr << "SCCP: Don't know how to handle: " << I;
- markOverdefined(&I); // Just in case
+ // If a new instruction is added to LLVM that we don't handle.
+ dbgs() << "SCCP: Don't know how to handle: " << I;
+ markAnythingOverdefined(&I); // Just in case
}
};
+} // end anonymous namespace
+
+
// getFeasibleSuccessors - Return a vector of booleans to indicate which
// successors are reachable from a given terminator instruction.
//
void SCCPSolver::getFeasibleSuccessors(TerminatorInst &TI,
- std::vector<bool> &Succs) {
+ SmallVector<bool, 16> &Succs) {
Succs.resize(TI.getNumSuccessors());
if (BranchInst *BI = dyn_cast<BranchInst>(&TI)) {
if (BI->isUnconditional()) {
Succs[0] = true;
- } else {
- LatticeVal &BCValue = getValueState(BI->getCondition());
- if (BCValue.isOverdefined() ||
- (BCValue.isConstant() && !isa<ConstantBool>(BCValue.getConstant()))) {
- // Overdefined condition variables, and branches on unfoldable constant
- // conditions, mean the branch could go either way.
+ return;
+ }
+
+ LatticeVal BCValue = getValueState(BI->getCondition());
+ ConstantInt *CI = BCValue.getConstantInt();
+ if (CI == 0) {
+ // Overdefined condition variables, and branches on unfoldable constant
+ // conditions, mean the branch could go either way.
+ if (!BCValue.isUndefined())
Succs[0] = Succs[1] = true;
- } else if (BCValue.isConstant()) {
- // Constant condition variables mean the branch can only go a single way
- Succs[BCValue.getConstant() == ConstantBool::False] = true;
- }
+ return;
}
- } else if (InvokeInst *II = dyn_cast<InvokeInst>(&TI)) {
+
+ // Constant condition variables mean the branch can only go a single way.
+ Succs[CI->isZero()] = true;
+ return;
+ }
+
+ if (isa<InvokeInst>(TI)) {
// Invoke instructions successors are always executable.
Succs[0] = Succs[1] = true;
- } else if (SwitchInst *SI = dyn_cast<SwitchInst>(&TI)) {
- LatticeVal &SCValue = getValueState(SI->getCondition());
- if (SCValue.isOverdefined() || // Overdefined condition?
- (SCValue.isConstant() && !isa<ConstantInt>(SCValue.getConstant()))) {
+ return;
+ }
+
+ if (SwitchInst *SI = dyn_cast<SwitchInst>(&TI)) {
+ LatticeVal SCValue = getValueState(SI->getCondition());
+ ConstantInt *CI = SCValue.getConstantInt();
+
+ if (CI == 0) { // Overdefined or undefined condition?
// All destinations are executable!
- Succs.assign(TI.getNumSuccessors(), true);
- } else if (SCValue.isConstant()) {
- Constant *CPV = SCValue.getConstant();
- // Make sure to skip the "default value" which isn't a value
- for (unsigned i = 1, E = SI->getNumSuccessors(); i != E; ++i) {
- if (SI->getSuccessorValue(i) == CPV) {// Found the right branch...
- Succs[i] = true;
- return;
- }
- }
-
- // Constant value not equal to any of the branches... must execute
- // default branch then...
- Succs[0] = true;
+ if (!SCValue.isUndefined())
+ Succs.assign(TI.getNumSuccessors(), true);
+ return;
}
- } else {
- std::cerr << "SCCP: Don't know how to handle: " << TI;
+
+ Succs[SI->findCaseValue(CI)] = true;
+ return;
+ }
+
+ // TODO: This could be improved if the operand is a [cast of a] BlockAddress.
+ if (isa<IndirectBrInst>(&TI)) {
+ // Just mark all destinations executable!
Succs.assign(TI.getNumSuccessors(), true);
+ return;
}
+
+#ifndef NDEBUG
+ dbgs() << "Unknown terminator instruction: " << TI << '\n';
+#endif
+ llvm_unreachable("SCCP: Don't know how to handle this terminator!");
}
// isEdgeFeasible - Return true if the control flow edge from the 'From' basic
-// block to the 'To' basic block is currently feasible...
+// block to the 'To' basic block is currently feasible.
//
bool SCCPSolver::isEdgeFeasible(BasicBlock *From, BasicBlock *To) {
assert(BBExecutable.count(To) && "Dest should always be alive!");
// Make sure the source basic block is executable!!
if (!BBExecutable.count(From)) return false;
-
- // Check to make sure this edge itself is actually feasible now...
+
+ // Check to make sure this edge itself is actually feasible now.
TerminatorInst *TI = From->getTerminator();
if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
if (BI->isUnconditional())
return true;
- else {
- LatticeVal &BCValue = getValueState(BI->getCondition());
- if (BCValue.isOverdefined()) {
- // Overdefined condition variables mean the branch could go either way.
- return true;
- } else if (BCValue.isConstant()) {
- // Not branching on an evaluatable constant?
- if (!isa<ConstantBool>(BCValue.getConstant())) return true;
+
+ LatticeVal BCValue = getValueState(BI->getCondition());
- // Constant condition variables mean the branch can only go a single way
- return BI->getSuccessor(BCValue.getConstant() ==
- ConstantBool::False) == To;
- }
- return false;
- }
- } else if (InvokeInst *II = dyn_cast<InvokeInst>(TI)) {
- // Invoke instructions successors are always executable.
+ // Overdefined condition variables mean the branch could go either way,
+ // undef conditions mean that neither edge is feasible yet.
+ ConstantInt *CI = BCValue.getConstantInt();
+ if (CI == 0)
+ return !BCValue.isUndefined();
+
+ // Constant condition variables mean the branch can only go a single way.
+ return BI->getSuccessor(CI->isZero()) == To;
+ }
+
+ // Invoke instructions successors are always executable.
+ if (isa<InvokeInst>(TI))
return true;
- } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
- LatticeVal &SCValue = getValueState(SI->getCondition());
- if (SCValue.isOverdefined()) { // Overdefined condition?
- // All destinations are executable!
- return true;
- } else if (SCValue.isConstant()) {
- Constant *CPV = SCValue.getConstant();
- if (!isa<ConstantInt>(CPV))
- return true; // not a foldable constant?
-
- // Make sure to skip the "default value" which isn't a value
- for (unsigned i = 1, E = SI->getNumSuccessors(); i != E; ++i)
- if (SI->getSuccessorValue(i) == CPV) // Found the taken branch...
- return SI->getSuccessor(i) == To;
-
- // Constant value not equal to any of the branches... must execute
- // default branch then...
- return SI->getDefaultDest() == To;
- }
- return false;
- } else {
- std::cerr << "Unknown terminator instruction: " << *TI;
- abort();
+
+ if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
+ LatticeVal SCValue = getValueState(SI->getCondition());
+ ConstantInt *CI = SCValue.getConstantInt();
+
+ if (CI == 0)
+ return !SCValue.isUndefined();
+
+ // Make sure to skip the "default value" which isn't a value
+ for (unsigned i = 1, E = SI->getNumSuccessors(); i != E; ++i)
+ if (SI->getSuccessorValue(i) == CI) // Found the taken branch.
+ return SI->getSuccessor(i) == To;
+
+ // If the constant value is not equal to any of the branches, we must
+ // execute default branch.
+ return SI->getDefaultDest() == To;
}
+
+ // Just mark all destinations executable!
+ // TODO: This could be improved if the operand is a [cast of a] BlockAddress.
+ if (isa<IndirectBrInst>(&TI))
+ return true;
+
+#ifndef NDEBUG
+ dbgs() << "Unknown terminator instruction: " << *TI << '\n';
+#endif
+ llvm_unreachable(0);
}
-// visit Implementations - Something changed in this instruction... Either an
+// visit Implementations - Something changed in this instruction, either an
// operand made a transition, or the instruction is newly executable. Change
// the value type of I to reflect these changes if appropriate. This method
// makes sure to do the following actions:
// successors executable.
//
void SCCPSolver::visitPHINode(PHINode &PN) {
- LatticeVal &PNIV = getValueState(&PN);
- if (PNIV.isOverdefined()) {
+ // If this PN returns a struct, just mark the result overdefined.
+ // TODO: We could do a lot better than this if code actually uses this.
+ if (PN.getType()->isStructTy())
+ return markAnythingOverdefined(&PN);
+
+ if (getValueState(&PN).isOverdefined()) {
// There may be instructions using this PHI node that are not overdefined
// themselves. If so, make sure that they know that the PHI node operand
// changed.
std::multimap<PHINode*, Instruction*>::iterator I, E;
tie(I, E) = UsersOfOverdefinedPHIs.equal_range(&PN);
- if (I != E) {
- std::vector<Instruction*> Users;
- Users.reserve(std::distance(I, E));
- for (; I != E; ++I) Users.push_back(I->second);
- while (!Users.empty()) {
- visit(Users.back());
- Users.pop_back();
- }
- }
+ if (I == E)
+ return;
+
+ SmallVector<Instruction*, 16> Users;
+ for (; I != E; ++I)
+ Users.push_back(I->second);
+ while (!Users.empty())
+ visit(Users.pop_back_val());
return; // Quick exit
}
// Super-extra-high-degree PHI nodes are unlikely to ever be marked constant,
// and slow us down a lot. Just mark them overdefined.
- if (PN.getNumIncomingValues() > 64) {
- markOverdefined(PNIV, &PN);
- return;
- }
-
+ if (PN.getNumIncomingValues() > 64)
+ return markOverdefined(&PN);
+
// Look at all of the executable operands of the PHI node. If any of them
// are overdefined, the PHI becomes overdefined as well. If they are all
// constant, and they agree with each other, the PHI becomes the identical
//
Constant *OperandVal = 0;
for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
- LatticeVal &IV = getValueState(PN.getIncomingValue(i));
+ LatticeVal IV = getValueState(PN.getIncomingValue(i));
if (IV.isUndefined()) continue; // Doesn't influence PHI node.
+
+ if (!isEdgeFeasible(PN.getIncomingBlock(i), PN.getParent()))
+ continue;
- if (isEdgeFeasible(PN.getIncomingBlock(i), PN.getParent())) {
- if (IV.isOverdefined()) { // PHI node becomes overdefined!
- markOverdefined(PNIV, &PN);
- return;
- }
+ if (IV.isOverdefined()) // PHI node becomes overdefined!
+ return markOverdefined(&PN);
- if (OperandVal == 0) { // Grab the first value...
- OperandVal = IV.getConstant();
- } else { // Another value is being merged in!
- // There is already a reachable operand. If we conflict with it,
- // then the PHI node becomes overdefined. If we agree with it, we
- // can continue on.
-
- // Check to see if there are two different constants merging...
- if (IV.getConstant() != OperandVal) {
- // Yes there is. This means the PHI node is not constant.
- // You must be overdefined poor PHI.
- //
- markOverdefined(PNIV, &PN); // The PHI node now becomes overdefined
- return; // I'm done analyzing you
- }
- }
+ if (OperandVal == 0) { // Grab the first value.
+ OperandVal = IV.getConstant();
+ continue;
}
+
+ // There is already a reachable operand. If we conflict with it,
+ // then the PHI node becomes overdefined. If we agree with it, we
+ // can continue on.
+
+ // Check to see if there are two different constants merging, if so, the PHI
+ // node is overdefined.
+ if (IV.getConstant() != OperandVal)
+ return markOverdefined(&PN);
}
// If we exited the loop, this means that the PHI node only has constant
// this is the case, the PHI remains undefined.
//
if (OperandVal)
- markConstant(PNIV, &PN, OperandVal); // Acquire operand value
+ markConstant(&PN, OperandVal); // Acquire operand value
}
+
+
+
void SCCPSolver::visitReturnInst(ReturnInst &I) {
- if (I.getNumOperands() == 0) return; // Ret void
+ if (I.getNumOperands() == 0) return; // ret void
- // If we are tracking the return value of this function, merge it in.
Function *F = I.getParent()->getParent();
- if (F->hasInternalLinkage() && !TrackedFunctionRetVals.empty()) {
- hash_map<Function*, LatticeVal>::iterator TFRVI =
- TrackedFunctionRetVals.find(F);
- if (TFRVI != TrackedFunctionRetVals.end() &&
- !TFRVI->second.isOverdefined()) {
- LatticeVal &IV = getValueState(I.getOperand(0));
- mergeInValue(TFRVI->second, F, IV);
+ Value *ResultOp = I.getOperand(0);
+
+ // If we are tracking the return value of this function, merge it in.
+ if (!TrackedRetVals.empty() && !ResultOp->getType()->isStructTy()) {
+ DenseMap<Function*, LatticeVal>::iterator TFRVI =
+ TrackedRetVals.find(F);
+ if (TFRVI != TrackedRetVals.end()) {
+ mergeInValue(TFRVI->second, F, getValueState(ResultOp));
+ return;
}
}
+
+ // Handle functions that return multiple values.
+ if (!TrackedMultipleRetVals.empty()) {
+ if (const StructType *STy = dyn_cast<StructType>(ResultOp->getType()))
+ if (MRVFunctionsTracked.count(F))
+ for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
+ mergeInValue(TrackedMultipleRetVals[std::make_pair(F, i)], F,
+ getStructValueState(ResultOp, i));
+
+ }
}
-
void SCCPSolver::visitTerminatorInst(TerminatorInst &TI) {
- std::vector<bool> SuccFeasible;
+ SmallVector<bool, 16> SuccFeasible;
getFeasibleSuccessors(TI, SuccFeasible);
BasicBlock *BB = TI.getParent();
- // Mark all feasible successors executable...
+ // Mark all feasible successors executable.
for (unsigned i = 0, e = SuccFeasible.size(); i != e; ++i)
if (SuccFeasible[i])
markEdgeExecutable(BB, TI.getSuccessor(i));
}
void SCCPSolver::visitCastInst(CastInst &I) {
- Value *V = I.getOperand(0);
- LatticeVal &VState = getValueState(V);
- if (VState.isOverdefined()) // Inherit overdefinedness of operand
+ LatticeVal OpSt = getValueState(I.getOperand(0));
+ if (OpSt.isOverdefined()) // Inherit overdefinedness of operand
markOverdefined(&I);
- else if (VState.isConstant()) // Propagate constant value
- markConstant(&I, ConstantExpr::getCast(VState.getConstant(), I.getType()));
+ else if (OpSt.isConstant()) // Propagate constant value
+ markConstant(&I, ConstantExpr::getCast(I.getOpcode(),
+ OpSt.getConstant(), I.getType()));
+}
+
+
+void SCCPSolver::visitExtractValueInst(ExtractValueInst &EVI) {
+ // If this returns a struct, mark all elements over defined, we don't track
+ // structs in structs.
+ if (EVI.getType()->isStructTy())
+ return markAnythingOverdefined(&EVI);
+
+ // If this is extracting from more than one level of struct, we don't know.
+ if (EVI.getNumIndices() != 1)
+ return markOverdefined(&EVI);
+
+ Value *AggVal = EVI.getAggregateOperand();
+ if (AggVal->getType()->isStructTy()) {
+ unsigned i = *EVI.idx_begin();
+ LatticeVal EltVal = getStructValueState(AggVal, i);
+ mergeInValue(getValueState(&EVI), &EVI, EltVal);
+ } else {
+ // Otherwise, must be extracting from an array.
+ return markOverdefined(&EVI);
+ }
+}
+
+void SCCPSolver::visitInsertValueInst(InsertValueInst &IVI) {
+ const StructType *STy = dyn_cast<StructType>(IVI.getType());
+ if (STy == 0)
+ return markOverdefined(&IVI);
+
+ // If this has more than one index, we can't handle it, drive all results to
+ // undef.
+ if (IVI.getNumIndices() != 1)
+ return markAnythingOverdefined(&IVI);
+
+ Value *Aggr = IVI.getAggregateOperand();
+ unsigned Idx = *IVI.idx_begin();
+
+ // Compute the result based on what we're inserting.
+ for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
+ // This passes through all values that aren't the inserted element.
+ if (i != Idx) {
+ LatticeVal EltVal = getStructValueState(Aggr, i);
+ mergeInValue(getStructValueState(&IVI, i), &IVI, EltVal);
+ continue;
+ }
+
+ Value *Val = IVI.getInsertedValueOperand();
+ if (Val->getType()->isStructTy())
+ // We don't track structs in structs.
+ markOverdefined(getStructValueState(&IVI, i), &IVI);
+ else {
+ LatticeVal InVal = getValueState(Val);
+ mergeInValue(getStructValueState(&IVI, i), &IVI, InVal);
+ }
+ }
}
void SCCPSolver::visitSelectInst(SelectInst &I) {
- LatticeVal &CondValue = getValueState(I.getCondition());
- if (CondValue.isOverdefined())
- markOverdefined(&I);
- else if (CondValue.isConstant()) {
- if (CondValue.getConstant() == ConstantBool::True) {
- LatticeVal &Val = getValueState(I.getTrueValue());
- if (Val.isOverdefined())
- markOverdefined(&I);
- else if (Val.isConstant())
- markConstant(&I, Val.getConstant());
- } else if (CondValue.getConstant() == ConstantBool::False) {
- LatticeVal &Val = getValueState(I.getFalseValue());
- if (Val.isOverdefined())
- markOverdefined(&I);
- else if (Val.isConstant())
- markConstant(&I, Val.getConstant());
- } else
- markOverdefined(&I);
+ // If this select returns a struct, just mark the result overdefined.
+ // TODO: We could do a lot better than this if code actually uses this.
+ if (I.getType()->isStructTy())
+ return markAnythingOverdefined(&I);
+
+ LatticeVal CondValue = getValueState(I.getCondition());
+ if (CondValue.isUndefined())
+ return;
+
+ if (ConstantInt *CondCB = CondValue.getConstantInt()) {
+ Value *OpVal = CondCB->isZero() ? I.getFalseValue() : I.getTrueValue();
+ mergeInValue(&I, getValueState(OpVal));
+ return;
}
+
+ // Otherwise, the condition is overdefined or a constant we can't evaluate.
+ // See if we can produce something better than overdefined based on the T/F
+ // value.
+ LatticeVal TVal = getValueState(I.getTrueValue());
+ LatticeVal FVal = getValueState(I.getFalseValue());
+
+ // select ?, C, C -> C.
+ if (TVal.isConstant() && FVal.isConstant() &&
+ TVal.getConstant() == FVal.getConstant())
+ return markConstant(&I, FVal.getConstant());
+
+ if (TVal.isUndefined()) // select ?, undef, X -> X.
+ return mergeInValue(&I, FVal);
+ if (FVal.isUndefined()) // select ?, X, undef -> X.
+ return mergeInValue(&I, TVal);
+ markOverdefined(&I);
}
-// Handle BinaryOperators and Shift Instructions...
+// Handle Binary Operators.
void SCCPSolver::visitBinaryOperator(Instruction &I) {
+ LatticeVal V1State = getValueState(I.getOperand(0));
+ LatticeVal V2State = getValueState(I.getOperand(1));
+
LatticeVal &IV = ValueState[&I];
if (IV.isOverdefined()) return;
- LatticeVal &V1State = getValueState(I.getOperand(0));
- LatticeVal &V2State = getValueState(I.getOperand(1));
-
- if (V1State.isOverdefined() || V2State.isOverdefined()) {
- // If both operands are PHI nodes, it is possible that this instruction has
- // a constant value, despite the fact that the PHI node doesn't. Check for
- // this condition now.
- if (PHINode *PN1 = dyn_cast<PHINode>(I.getOperand(0)))
- if (PHINode *PN2 = dyn_cast<PHINode>(I.getOperand(1)))
- if (PN1->getParent() == PN2->getParent()) {
- // Since the two PHI nodes are in the same basic block, they must have
- // entries for the same predecessors. Walk the predecessor list, and
- // if all of the incoming values are constants, and the result of
- // evaluating this expression with all incoming value pairs is the
- // same, then this expression is a constant even though the PHI node
- // is not a constant!
- LatticeVal Result;
- for (unsigned i = 0, e = PN1->getNumIncomingValues(); i != e; ++i) {
- LatticeVal &In1 = getValueState(PN1->getIncomingValue(i));
- BasicBlock *InBlock = PN1->getIncomingBlock(i);
- LatticeVal &In2 =
- getValueState(PN2->getIncomingValueForBlock(InBlock));
-
- if (In1.isOverdefined() || In2.isOverdefined()) {
+ if (V1State.isConstant() && V2State.isConstant())
+ return markConstant(IV, &I,
+ ConstantExpr::get(I.getOpcode(), V1State.getConstant(),
+ V2State.getConstant()));
+
+ // If something is undef, wait for it to resolve.
+ if (!V1State.isOverdefined() && !V2State.isOverdefined())
+ return;
+
+ // Otherwise, one of our operands is overdefined. Try to produce something
+ // better than overdefined with some tricks.
+
+ // If this is an AND or OR with 0 or -1, it doesn't matter that the other
+ // operand is overdefined.
+ if (I.getOpcode() == Instruction::And || I.getOpcode() == Instruction::Or) {
+ LatticeVal *NonOverdefVal = 0;
+ if (!V1State.isOverdefined())
+ NonOverdefVal = &V1State;
+ else if (!V2State.isOverdefined())
+ NonOverdefVal = &V2State;
+
+ if (NonOverdefVal) {
+ if (NonOverdefVal->isUndefined()) {
+ // Could annihilate value.
+ if (I.getOpcode() == Instruction::And)
+ markConstant(IV, &I, Constant::getNullValue(I.getType()));
+ else if (const VectorType *PT = dyn_cast<VectorType>(I.getType()))
+ markConstant(IV, &I, Constant::getAllOnesValue(PT));
+ else
+ markConstant(IV, &I,
+ Constant::getAllOnesValue(I.getType()));
+ return;
+ }
+
+ if (I.getOpcode() == Instruction::And) {
+ // X and 0 = 0
+ if (NonOverdefVal->getConstant()->isNullValue())
+ return markConstant(IV, &I, NonOverdefVal->getConstant());
+ } else {
+ if (ConstantInt *CI = NonOverdefVal->getConstantInt())
+ if (CI->isAllOnesValue()) // X or -1 = -1
+ return markConstant(IV, &I, NonOverdefVal->getConstant());
+ }
+ }
+ }
+
+
+ // If both operands are PHI nodes, it is possible that this instruction has
+ // a constant value, despite the fact that the PHI node doesn't. Check for
+ // this condition now.
+ if (PHINode *PN1 = dyn_cast<PHINode>(I.getOperand(0)))
+ if (PHINode *PN2 = dyn_cast<PHINode>(I.getOperand(1)))
+ if (PN1->getParent() == PN2->getParent()) {
+ // Since the two PHI nodes are in the same basic block, they must have
+ // entries for the same predecessors. Walk the predecessor list, and
+ // if all of the incoming values are constants, and the result of
+ // evaluating this expression with all incoming value pairs is the
+ // same, then this expression is a constant even though the PHI node
+ // is not a constant!
+ LatticeVal Result;
+ for (unsigned i = 0, e = PN1->getNumIncomingValues(); i != e; ++i) {
+ LatticeVal In1 = getValueState(PN1->getIncomingValue(i));
+ BasicBlock *InBlock = PN1->getIncomingBlock(i);
+ LatticeVal In2 =getValueState(PN2->getIncomingValueForBlock(InBlock));
+
+ if (In1.isOverdefined() || In2.isOverdefined()) {
+ Result.markOverdefined();
+ break; // Cannot fold this operation over the PHI nodes!
+ }
+
+ if (In1.isConstant() && In2.isConstant()) {
+ Constant *V = ConstantExpr::get(I.getOpcode(), In1.getConstant(),
+ In2.getConstant());
+ if (Result.isUndefined())
+ Result.markConstant(V);
+ else if (Result.isConstant() && Result.getConstant() != V) {
Result.markOverdefined();
- break; // Cannot fold this operation over the PHI nodes!
- } else if (In1.isConstant() && In2.isConstant()) {
- Constant *V = ConstantExpr::get(I.getOpcode(), In1.getConstant(),
- In2.getConstant());
- if (Result.isUndefined())
- Result.markConstant(V);
- else if (Result.isConstant() && Result.getConstant() != V) {
- Result.markOverdefined();
- break;
- }
+ break;
}
}
+ }
- // If we found a constant value here, then we know the instruction is
- // constant despite the fact that the PHI nodes are overdefined.
- if (Result.isConstant()) {
- markConstant(IV, &I, Result.getConstant());
- // Remember that this instruction is virtually using the PHI node
- // operands.
- UsersOfOverdefinedPHIs.insert(std::make_pair(PN1, &I));
- UsersOfOverdefinedPHIs.insert(std::make_pair(PN2, &I));
- return;
- } else if (Result.isUndefined()) {
- return;
- }
+ // If we found a constant value here, then we know the instruction is
+ // constant despite the fact that the PHI nodes are overdefined.
+ if (Result.isConstant()) {
+ markConstant(IV, &I, Result.getConstant());
+ // Remember that this instruction is virtually using the PHI node
+ // operands.
+ InsertInOverdefinedPHIs(&I, PN1);
+ InsertInOverdefinedPHIs(&I, PN2);
+ return;
+ }
+
+ if (Result.isUndefined())
+ return;
+
+ // Okay, this really is overdefined now. Since we might have
+ // speculatively thought that this was not overdefined before, and
+ // added ourselves to the UsersOfOverdefinedPHIs list for the PHIs,
+ // make sure to clean out any entries that we put there, for
+ // efficiency.
+ RemoveFromOverdefinedPHIs(&I, PN1);
+ RemoveFromOverdefinedPHIs(&I, PN2);
+ }
- // Okay, this really is overdefined now. Since we might have
- // speculatively thought that this was not overdefined before, and
- // added ourselves to the UsersOfOverdefinedPHIs list for the PHIs,
- // make sure to clean out any entries that we put there, for
- // efficiency.
- std::multimap<PHINode*, Instruction*>::iterator It, E;
- tie(It, E) = UsersOfOverdefinedPHIs.equal_range(PN1);
- while (It != E) {
- if (It->second == &I) {
- UsersOfOverdefinedPHIs.erase(It++);
- } else
- ++It;
+ markOverdefined(&I);
+}
+
+// Handle ICmpInst instruction.
+void SCCPSolver::visitCmpInst(CmpInst &I) {
+ LatticeVal V1State = getValueState(I.getOperand(0));
+ LatticeVal V2State = getValueState(I.getOperand(1));
+
+ LatticeVal &IV = ValueState[&I];
+ if (IV.isOverdefined()) return;
+
+ if (V1State.isConstant() && V2State.isConstant())
+ return markConstant(IV, &I, ConstantExpr::getCompare(I.getPredicate(),
+ V1State.getConstant(),
+ V2State.getConstant()));
+
+ // If operands are still undefined, wait for it to resolve.
+ if (!V1State.isOverdefined() && !V2State.isOverdefined())
+ return;
+
+ // If something is overdefined, use some tricks to avoid ending up and over
+ // defined if we can.
+
+ // If both operands are PHI nodes, it is possible that this instruction has
+ // a constant value, despite the fact that the PHI node doesn't. Check for
+ // this condition now.
+ if (PHINode *PN1 = dyn_cast<PHINode>(I.getOperand(0)))
+ if (PHINode *PN2 = dyn_cast<PHINode>(I.getOperand(1)))
+ if (PN1->getParent() == PN2->getParent()) {
+ // Since the two PHI nodes are in the same basic block, they must have
+ // entries for the same predecessors. Walk the predecessor list, and
+ // if all of the incoming values are constants, and the result of
+ // evaluating this expression with all incoming value pairs is the
+ // same, then this expression is a constant even though the PHI node
+ // is not a constant!
+ LatticeVal Result;
+ for (unsigned i = 0, e = PN1->getNumIncomingValues(); i != e; ++i) {
+ LatticeVal In1 = getValueState(PN1->getIncomingValue(i));
+ BasicBlock *InBlock = PN1->getIncomingBlock(i);
+ LatticeVal In2 =getValueState(PN2->getIncomingValueForBlock(InBlock));
+
+ if (In1.isOverdefined() || In2.isOverdefined()) {
+ Result.markOverdefined();
+ break; // Cannot fold this operation over the PHI nodes!
}
- tie(It, E) = UsersOfOverdefinedPHIs.equal_range(PN2);
- while (It != E) {
- if (It->second == &I) {
- UsersOfOverdefinedPHIs.erase(It++);
- } else
- ++It;
+
+ if (In1.isConstant() && In2.isConstant()) {
+ Constant *V = ConstantExpr::getCompare(I.getPredicate(),
+ In1.getConstant(),
+ In2.getConstant());
+ if (Result.isUndefined())
+ Result.markConstant(V);
+ else if (Result.isConstant() && Result.getConstant() != V) {
+ Result.markOverdefined();
+ break;
+ }
}
}
- markOverdefined(IV, &I);
- } else if (V1State.isConstant() && V2State.isConstant()) {
- markConstant(IV, &I, ConstantExpr::get(I.getOpcode(), V1State.getConstant(),
- V2State.getConstant()));
+ // If we found a constant value here, then we know the instruction is
+ // constant despite the fact that the PHI nodes are overdefined.
+ if (Result.isConstant()) {
+ markConstant(&I, Result.getConstant());
+ // Remember that this instruction is virtually using the PHI node
+ // operands.
+ InsertInOverdefinedPHIs(&I, PN1);
+ InsertInOverdefinedPHIs(&I, PN2);
+ return;
+ }
+
+ if (Result.isUndefined())
+ return;
+
+ // Okay, this really is overdefined now. Since we might have
+ // speculatively thought that this was not overdefined before, and
+ // added ourselves to the UsersOfOverdefinedPHIs list for the PHIs,
+ // make sure to clean out any entries that we put there, for
+ // efficiency.
+ RemoveFromOverdefinedPHIs(&I, PN1);
+ RemoveFromOverdefinedPHIs(&I, PN2);
+ }
+
+ markOverdefined(&I);
+}
+
+void SCCPSolver::visitExtractElementInst(ExtractElementInst &I) {
+ // TODO : SCCP does not handle vectors properly.
+ return markOverdefined(&I);
+
+#if 0
+ LatticeVal &ValState = getValueState(I.getOperand(0));
+ LatticeVal &IdxState = getValueState(I.getOperand(1));
+
+ if (ValState.isOverdefined() || IdxState.isOverdefined())
+ markOverdefined(&I);
+ else if(ValState.isConstant() && IdxState.isConstant())
+ markConstant(&I, ConstantExpr::getExtractElement(ValState.getConstant(),
+ IdxState.getConstant()));
+#endif
+}
+
+void SCCPSolver::visitInsertElementInst(InsertElementInst &I) {
+ // TODO : SCCP does not handle vectors properly.
+ return markOverdefined(&I);
+#if 0
+ LatticeVal &ValState = getValueState(I.getOperand(0));
+ LatticeVal &EltState = getValueState(I.getOperand(1));
+ LatticeVal &IdxState = getValueState(I.getOperand(2));
+
+ if (ValState.isOverdefined() || EltState.isOverdefined() ||
+ IdxState.isOverdefined())
+ markOverdefined(&I);
+ else if(ValState.isConstant() && EltState.isConstant() &&
+ IdxState.isConstant())
+ markConstant(&I, ConstantExpr::getInsertElement(ValState.getConstant(),
+ EltState.getConstant(),
+ IdxState.getConstant()));
+ else if (ValState.isUndefined() && EltState.isConstant() &&
+ IdxState.isConstant())
+ markConstant(&I,ConstantExpr::getInsertElement(UndefValue::get(I.getType()),
+ EltState.getConstant(),
+ IdxState.getConstant()));
+#endif
+}
+
+void SCCPSolver::visitShuffleVectorInst(ShuffleVectorInst &I) {
+ // TODO : SCCP does not handle vectors properly.
+ return markOverdefined(&I);
+#if 0
+ LatticeVal &V1State = getValueState(I.getOperand(0));
+ LatticeVal &V2State = getValueState(I.getOperand(1));
+ LatticeVal &MaskState = getValueState(I.getOperand(2));
+
+ if (MaskState.isUndefined() ||
+ (V1State.isUndefined() && V2State.isUndefined()))
+ return; // Undefined output if mask or both inputs undefined.
+
+ if (V1State.isOverdefined() || V2State.isOverdefined() ||
+ MaskState.isOverdefined()) {
+ markOverdefined(&I);
+ } else {
+ // A mix of constant/undef inputs.
+ Constant *V1 = V1State.isConstant() ?
+ V1State.getConstant() : UndefValue::get(I.getType());
+ Constant *V2 = V2State.isConstant() ?
+ V2State.getConstant() : UndefValue::get(I.getType());
+ Constant *Mask = MaskState.isConstant() ?
+ MaskState.getConstant() : UndefValue::get(I.getOperand(2)->getType());
+ markConstant(&I, ConstantExpr::getShuffleVector(V1, V2, Mask));
}
+#endif
}
-// Handle getelementptr instructions... if all operands are constants then we
+// Handle getelementptr instructions. If all operands are constants then we
// can turn this into a getelementptr ConstantExpr.
//
void SCCPSolver::visitGetElementPtrInst(GetElementPtrInst &I) {
- LatticeVal &IV = ValueState[&I];
- if (IV.isOverdefined()) return;
+ if (ValueState[&I].isOverdefined()) return;
- std::vector<Constant*> Operands;
+ SmallVector<Constant*, 8> Operands;
Operands.reserve(I.getNumOperands());
for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) {
- LatticeVal &State = getValueState(I.getOperand(i));
+ LatticeVal State = getValueState(I.getOperand(i));
if (State.isUndefined())
- return; // Operands are not resolved yet...
- else if (State.isOverdefined()) {
- markOverdefined(IV, &I);
- return;
- }
+ return; // Operands are not resolved yet.
+
+ if (State.isOverdefined())
+ return markOverdefined(&I);
+
assert(State.isConstant() && "Unknown state!");
Operands.push_back(State.getConstant());
}
Constant *Ptr = Operands[0];
- Operands.erase(Operands.begin()); // Erase the pointer from idx list...
-
- markConstant(IV, &I, ConstantExpr::getGetElementPtr(Ptr, Operands));
-}
-
-/// GetGEPGlobalInitializer - Given a constant and a getelementptr constantexpr,
-/// return the constant value being addressed by the constant expression, or
-/// null if something is funny.
-///
-static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
- if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
- return 0; // Do not allow stepping over the value!
-
- // Loop over all of the operands, tracking down which value we are
- // addressing...
- for (unsigned i = 2, e = CE->getNumOperands(); i != e; ++i)
- if (ConstantUInt *CU = dyn_cast<ConstantUInt>(CE->getOperand(i))) {
- ConstantStruct *CS = dyn_cast<ConstantStruct>(C);
- if (CS == 0) return 0;
- if (CU->getValue() >= CS->getNumOperands()) return 0;
- C = CS->getOperand(CU->getValue());
- } else if (ConstantSInt *CS = dyn_cast<ConstantSInt>(CE->getOperand(i))) {
- ConstantArray *CA = dyn_cast<ConstantArray>(C);
- if (CA == 0) return 0;
- if ((uint64_t)CS->getValue() >= CA->getNumOperands()) return 0;
- C = CA->getOperand(CS->getValue());
- } else
- return 0;
- return C;
+ markConstant(&I, ConstantExpr::getGetElementPtr(Ptr, &Operands[0]+1,
+ Operands.size()-1));
}
-void SCCPSolver::visitStoreInst(Instruction &SI) {
+void SCCPSolver::visitStoreInst(StoreInst &SI) {
+ // If this store is of a struct, ignore it.
+ if (SI.getOperand(0)->getType()->isStructTy())
+ return;
+
if (TrackedGlobals.empty() || !isa<GlobalVariable>(SI.getOperand(1)))
return;
+
GlobalVariable *GV = cast<GlobalVariable>(SI.getOperand(1));
- hash_map<GlobalVariable*, LatticeVal>::iterator I = TrackedGlobals.find(GV);
+ DenseMap<GlobalVariable*, LatticeVal>::iterator I = TrackedGlobals.find(GV);
if (I == TrackedGlobals.end() || I->second.isOverdefined()) return;
- // Get the value we are storing into the global.
- LatticeVal &PtrVal = getValueState(SI.getOperand(0));
-
- mergeInValue(I->second, GV, PtrVal);
+ // Get the value we are storing into the global, then merge it.
+ mergeInValue(I->second, GV, getValueState(SI.getOperand(0)));
if (I->second.isOverdefined())
TrackedGlobals.erase(I); // No need to keep tracking this!
}
// Handle load instructions. If the operand is a constant pointer to a constant
// global, we can replace the load with the loaded constant value!
void SCCPSolver::visitLoadInst(LoadInst &I) {
+ // If this load is of a struct, just mark the result overdefined.
+ if (I.getType()->isStructTy())
+ return markAnythingOverdefined(&I);
+
+ LatticeVal PtrVal = getValueState(I.getOperand(0));
+ if (PtrVal.isUndefined()) return; // The pointer is not resolved yet!
+
LatticeVal &IV = ValueState[&I];
if (IV.isOverdefined()) return;
- LatticeVal &PtrVal = getValueState(I.getOperand(0));
- if (PtrVal.isUndefined()) return; // The pointer is not resolved yet!
- if (PtrVal.isConstant() && !I.isVolatile()) {
- Value *Ptr = PtrVal.getConstant();
- if (isa<ConstantPointerNull>(Ptr)) {
- // load null -> null
- markConstant(IV, &I, Constant::getNullValue(I.getType()));
- return;
- }
-
- // Transform load (constant global) into the value loaded.
- if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) {
- if (GV->isConstant()) {
- if (!GV->isExternal()) {
- markConstant(IV, &I, GV->getInitializer());
- return;
- }
- } else if (!TrackedGlobals.empty()) {
- // If we are tracking this global, merge in the known value for it.
- hash_map<GlobalVariable*, LatticeVal>::iterator It =
- TrackedGlobals.find(GV);
- if (It != TrackedGlobals.end()) {
- mergeInValue(IV, &I, It->second);
- return;
- }
+ if (!PtrVal.isConstant() || I.isVolatile())
+ return markOverdefined(IV, &I);
+
+ Constant *Ptr = PtrVal.getConstant();
+
+ // load null -> null
+ if (isa<ConstantPointerNull>(Ptr) && I.getPointerAddressSpace() == 0)
+ return markConstant(IV, &I, Constant::getNullValue(I.getType()));
+
+ // Transform load (constant global) into the value loaded.
+ if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) {
+ if (!TrackedGlobals.empty()) {
+ // If we are tracking this global, merge in the known value for it.
+ DenseMap<GlobalVariable*, LatticeVal>::iterator It =
+ TrackedGlobals.find(GV);
+ if (It != TrackedGlobals.end()) {
+ mergeInValue(IV, &I, It->second);
+ return;
}
}
-
- // Transform load (constantexpr_GEP global, 0, ...) into the value loaded.
- if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
- if (CE->getOpcode() == Instruction::GetElementPtr)
- if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
- if (GV->isConstant() && !GV->isExternal())
- if (Constant *V =
- GetGEPGlobalInitializer(GV->getInitializer(), CE)) {
- markConstant(IV, &I, V);
- return;
- }
}
+ // Transform load from a constant into a constant if possible.
+ if (Constant *C = ConstantFoldLoadFromConstPtr(Ptr, TD))
+ return markConstant(IV, &I, C);
+
// Otherwise we cannot say for certain what value this load will produce.
// Bail out.
markOverdefined(IV, &I);
void SCCPSolver::visitCallSite(CallSite CS) {
Function *F = CS.getCalledFunction();
-
- // If we are tracking this function, we must make sure to bind arguments as
- // appropriate.
- hash_map<Function*, LatticeVal>::iterator TFRVI =TrackedFunctionRetVals.end();
- if (F && F->hasInternalLinkage())
- TFRVI = TrackedFunctionRetVals.find(F);
+ Instruction *I = CS.getInstruction();
- if (TFRVI != TrackedFunctionRetVals.end()) {
- // If this is the first call to the function hit, mark its entry block
- // executable.
- if (!BBExecutable.count(F->begin()))
- MarkBlockExecutable(F->begin());
+ // The common case is that we aren't tracking the callee, either because we
+ // are not doing interprocedural analysis or the callee is indirect, or is
+ // external. Handle these cases first.
+ if (F == 0 || F->isDeclaration()) {
+CallOverdefined:
+ // Void return and not tracking callee, just bail.
+ if (I->getType()->isVoidTy()) return;
+
+ // Otherwise, if we have a single return value case, and if the function is
+ // a declaration, maybe we can constant fold it.
+ if (F && F->isDeclaration() && !I->getType()->isStructTy() &&
+ canConstantFoldCallTo(F)) {
+
+ SmallVector<Constant*, 8> Operands;
+ for (CallSite::arg_iterator AI = CS.arg_begin(), E = CS.arg_end();
+ AI != E; ++AI) {
+ LatticeVal State = getValueState(*AI);
+
+ if (State.isUndefined())
+ return; // Operands are not resolved yet.
+ if (State.isOverdefined())
+ return markOverdefined(I);
+ assert(State.isConstant() && "Unknown state!");
+ Operands.push_back(State.getConstant());
+ }
+
+ // If we can constant fold this, mark the result of the call as a
+ // constant.
+ if (Constant *C = ConstantFoldCall(F, Operands.data(), Operands.size()))
+ return markConstant(I, C);
+ }
+
+ // Otherwise, we don't know anything about this call, mark it overdefined.
+ return markAnythingOverdefined(I);
+ }
+ // If this is a local function that doesn't have its address taken, mark its
+ // entry block executable and merge in the actual arguments to the call into
+ // the formal arguments of the function.
+ if (!TrackingIncomingArguments.empty() && TrackingIncomingArguments.count(F)){
+ MarkBlockExecutable(F->begin());
+
+ // Propagate information from this call site into the callee.
CallSite::arg_iterator CAI = CS.arg_begin();
- for (Function::aiterator AI = F->abegin(), E = F->aend();
+ for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
AI != E; ++AI, ++CAI) {
- LatticeVal &IV = ValueState[AI];
- if (!IV.isOverdefined())
- mergeInValue(IV, AI, getValueState(*CAI));
+ // If this argument is byval, and if the function is not readonly, there
+ // will be an implicit copy formed of the input aggregate.
+ if (AI->hasByValAttr() && !F->onlyReadsMemory()) {
+ markOverdefined(AI);
+ continue;
+ }
+
+ if (const StructType *STy = dyn_cast<StructType>(AI->getType())) {
+ for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
+ LatticeVal CallArg = getStructValueState(*CAI, i);
+ mergeInValue(getStructValueState(AI, i), AI, CallArg);
+ }
+ } else {
+ mergeInValue(AI, getValueState(*CAI));
+ }
}
}
- Instruction *I = CS.getInstruction();
- if (I->getType() == Type::VoidTy) return;
-
- LatticeVal &IV = ValueState[I];
- if (IV.isOverdefined()) return;
-
- // Propagate the return value of the function to the value of the instruction.
- if (TFRVI != TrackedFunctionRetVals.end()) {
- mergeInValue(IV, I, TFRVI->second);
- return;
- }
- if (F == 0 || !F->isExternal() || !canConstantFoldCallTo(F)) {
- markOverdefined(IV, I);
- return;
- }
-
- std::vector<Constant*> Operands;
- Operands.reserve(I->getNumOperands()-1);
-
- for (CallSite::arg_iterator AI = CS.arg_begin(), E = CS.arg_end();
- AI != E; ++AI) {
- LatticeVal &State = getValueState(*AI);
- if (State.isUndefined())
- return; // Operands are not resolved yet...
- else if (State.isOverdefined()) {
- markOverdefined(IV, I);
- return;
- }
- assert(State.isConstant() && "Unknown state!");
- Operands.push_back(State.getConstant());
+ // If this is a single/zero retval case, see if we're tracking the function.
+ if (const StructType *STy = dyn_cast<StructType>(F->getReturnType())) {
+ if (!MRVFunctionsTracked.count(F))
+ goto CallOverdefined; // Not tracking this callee.
+
+ // If we are tracking this callee, propagate the result of the function
+ // into this call site.
+ for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
+ mergeInValue(getStructValueState(I, i), I,
+ TrackedMultipleRetVals[std::make_pair(F, i)]);
+ } else {
+ DenseMap<Function*, LatticeVal>::iterator TFRVI = TrackedRetVals.find(F);
+ if (TFRVI == TrackedRetVals.end())
+ goto CallOverdefined; // Not tracking this callee.
+
+ // If so, propagate the return value of the callee into this call result.
+ mergeInValue(I, TFRVI->second);
}
-
- if (Constant *C = ConstantFoldCall(F, Operands))
- markConstant(IV, I, C);
- else
- markOverdefined(IV, I);
}
-
void SCCPSolver::Solve() {
// Process the work lists until they are empty!
- while (!BBWorkList.empty() || !InstWorkList.empty() ||
- !OverdefinedInstWorkList.empty()) {
- // Process the instruction work list...
+ while (!BBWorkList.empty() || !InstWorkList.empty() ||
+ !OverdefinedInstWorkList.empty()) {
+ // Process the overdefined instruction's work list first, which drives other
+ // things to overdefined more quickly.
while (!OverdefinedInstWorkList.empty()) {
- Value *I = OverdefinedInstWorkList.back();
- OverdefinedInstWorkList.pop_back();
+ Value *I = OverdefinedInstWorkList.pop_back_val();
+
+ DEBUG(dbgs() << "\nPopped off OI-WL: " << *I << '\n');
- DEBUG(std::cerr << "\nPopped off OI-WL: " << *I);
-
// "I" got into the work list because it either made the transition from
// bottom to constant
//
// Anything on this worklist that is overdefined need not be visited
// since all of its users will have already been marked as overdefined
- // Update all of the users of this instruction's value...
+ // Update all of the users of this instruction's value.
//
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
UI != E; ++UI)
- OperandChangedState(*UI);
+ if (Instruction *I = dyn_cast<Instruction>(*UI))
+ OperandChangedState(I);
}
- // Process the instruction work list...
+
+ // Process the instruction work list.
while (!InstWorkList.empty()) {
- Value *I = InstWorkList.back();
- InstWorkList.pop_back();
+ Value *I = InstWorkList.pop_back_val();
- DEBUG(std::cerr << "\nPopped off I-WL: " << *I);
-
- // "I" got into the work list because it either made the transition from
- // bottom to constant
+ DEBUG(dbgs() << "\nPopped off I-WL: " << *I << '\n');
+
+ // "I" got into the work list because it made the transition from undef to
+ // constant.
//
// Anything on this worklist that is overdefined need not be visited
// since all of its users will have already been marked as overdefined.
- // Update all of the users of this instruction's value...
+ // Update all of the users of this instruction's value.
//
- if (!getValueState(I).isOverdefined())
+ if (I->getType()->isStructTy() || !getValueState(I).isOverdefined())
for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
UI != E; ++UI)
- OperandChangedState(*UI);
+ if (Instruction *I = dyn_cast<Instruction>(*UI))
+ OperandChangedState(I);
}
-
- // Process the basic block work list...
+
+ // Process the basic block work list.
while (!BBWorkList.empty()) {
BasicBlock *BB = BBWorkList.back();
BBWorkList.pop_back();
-
- DEBUG(std::cerr << "\nPopped off BBWL: " << *BB);
-
+
+ DEBUG(dbgs() << "\nPopped off BBWL: " << *BB << '\n');
+
// Notify all instructions in this basic block that they are newly
// executable.
visit(BB);
}
}
-/// ResolveBranchesIn - While solving the dataflow for a function, we assume
+/// ResolvedUndefsIn - While solving the dataflow for a function, we assume
/// that branches on undef values cannot reach any of their successors.
/// However, this is not a safe assumption. After we solve dataflow, this
/// method should be use to handle this. If this returns true, the solver
/// should be rerun.
-bool SCCPSolver::ResolveBranchesIn(Function &F) {
- bool BranchesResolved = false;
+///
+/// This method handles this by finding an unresolved branch and marking it one
+/// of the edges from the block as being feasible, even though the condition
+/// doesn't say it would otherwise be. This allows SCCP to find the rest of the
+/// CFG and only slightly pessimizes the analysis results (by marking one,
+/// potentially infeasible, edge feasible). This cannot usefully modify the
+/// constraints on the condition of the branch, as that would impact other users
+/// of the value.
+///
+/// This scan also checks for values that use undefs, whose results are actually
+/// defined. For example, 'zext i8 undef to i32' should produce all zeros
+/// conservatively, as "(zext i8 X -> i32) & 0xFF00" must always return zero,
+/// even if X isn't defined.
+bool SCCPSolver::ResolvedUndefsIn(Function &F) {
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
+ if (!BBExecutable.count(BB))
+ continue;
+
+ for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
+ // Look for instructions which produce undef values.
+ if (I->getType()->isVoidTy()) continue;
+
+ if (const StructType *STy = dyn_cast<StructType>(I->getType())) {
+ // Only a few things that can be structs matter for undef. Just send
+ // all their results to overdefined. We could be more precise than this
+ // but it isn't worth bothering.
+ if (isa<CallInst>(I) || isa<SelectInst>(I)) {
+ for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
+ LatticeVal &LV = getStructValueState(I, i);
+ if (LV.isUndefined())
+ markOverdefined(LV, I);
+ }
+ }
+ continue;
+ }
+
+ LatticeVal &LV = getValueState(I);
+ if (!LV.isUndefined()) continue;
+
+ // No instructions using structs need disambiguation.
+ if (I->getOperand(0)->getType()->isStructTy())
+ continue;
+
+ // Get the lattice values of the first two operands for use below.
+ LatticeVal Op0LV = getValueState(I->getOperand(0));
+ LatticeVal Op1LV;
+ if (I->getNumOperands() == 2) {
+ // No instructions using structs need disambiguation.
+ if (I->getOperand(1)->getType()->isStructTy())
+ continue;
+
+ // If this is a two-operand instruction, and if both operands are
+ // undefs, the result stays undef.
+ Op1LV = getValueState(I->getOperand(1));
+ if (Op0LV.isUndefined() && Op1LV.isUndefined())
+ continue;
+ }
+
+ // If this is an instructions whose result is defined even if the input is
+ // not fully defined, propagate the information.
+ const Type *ITy = I->getType();
+ switch (I->getOpcode()) {
+ default: break; // Leave the instruction as an undef.
+ case Instruction::ZExt:
+ // After a zero extend, we know the top part is zero. SExt doesn't have
+ // to be handled here, because we don't know whether the top part is 1's
+ // or 0's.
+ case Instruction::SIToFP: // some FP values are not possible, just use 0.
+ case Instruction::UIToFP: // some FP values are not possible, just use 0.
+ markForcedConstant(I, Constant::getNullValue(ITy));
+ return true;
+ case Instruction::Mul:
+ case Instruction::And:
+ // undef * X -> 0. X could be zero.
+ // undef & X -> 0. X could be zero.
+ markForcedConstant(I, Constant::getNullValue(ITy));
+ return true;
+
+ case Instruction::Or:
+ // undef | X -> -1. X could be -1.
+ markForcedConstant(I, Constant::getAllOnesValue(ITy));
+ return true;
+
+ case Instruction::SDiv:
+ case Instruction::UDiv:
+ case Instruction::SRem:
+ case Instruction::URem:
+ // X / undef -> undef. No change.
+ // X % undef -> undef. No change.
+ if (Op1LV.isUndefined()) break;
+
+ // undef / X -> 0. X could be maxint.
+ // undef % X -> 0. X could be 1.
+ markForcedConstant(I, Constant::getNullValue(ITy));
+ return true;
+
+ case Instruction::AShr:
+ // undef >>s X -> undef. No change.
+ if (Op0LV.isUndefined()) break;
+
+ // X >>s undef -> X. X could be 0, X could have the high-bit known set.
+ if (Op0LV.isConstant())
+ markForcedConstant(I, Op0LV.getConstant());
+ else
+ markOverdefined(I);
+ return true;
+ case Instruction::LShr:
+ case Instruction::Shl:
+ // undef >> X -> undef. No change.
+ // undef << X -> undef. No change.
+ if (Op0LV.isUndefined()) break;
+
+ // X >> undef -> 0. X could be 0.
+ // X << undef -> 0. X could be 0.
+ markForcedConstant(I, Constant::getNullValue(ITy));
+ return true;
+ case Instruction::Select:
+ // undef ? X : Y -> X or Y. There could be commonality between X/Y.
+ if (Op0LV.isUndefined()) {
+ if (!Op1LV.isConstant()) // Pick the constant one if there is any.
+ Op1LV = getValueState(I->getOperand(2));
+ } else if (Op1LV.isUndefined()) {
+ // c ? undef : undef -> undef. No change.
+ Op1LV = getValueState(I->getOperand(2));
+ if (Op1LV.isUndefined())
+ break;
+ // Otherwise, c ? undef : x -> x.
+ } else {
+ // Leave Op1LV as Operand(1)'s LatticeValue.
+ }
+
+ if (Op1LV.isConstant())
+ markForcedConstant(I, Op1LV.getConstant());
+ else
+ markOverdefined(I);
+ return true;
+ case Instruction::Call:
+ // If a call has an undef result, it is because it is constant foldable
+ // but one of the inputs was undef. Just force the result to
+ // overdefined.
+ markOverdefined(I);
+ return true;
+ }
+ }
+
+ // Check to see if we have a branch or switch on an undefined value. If so
+ // we force the branch to go one way or the other to make the successor
+ // values live. It doesn't really matter which way we force it.
TerminatorInst *TI = BB->getTerminator();
if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
- if (BI->isConditional()) {
- LatticeVal &BCValue = getValueState(BI->getCondition());
- if (BCValue.isUndefined()) {
- BI->setCondition(ConstantBool::True);
- BranchesResolved = true;
- visit(BI);
- }
+ if (!BI->isConditional()) continue;
+ if (!getValueState(BI->getCondition()).isUndefined())
+ continue;
+
+ // If the input to SCCP is actually branch on undef, fix the undef to
+ // false.
+ if (isa<UndefValue>(BI->getCondition())) {
+ BI->setCondition(ConstantInt::getFalse(BI->getContext()));
+ markEdgeExecutable(BB, TI->getSuccessor(1));
+ return true;
}
- } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
- LatticeVal &SCValue = getValueState(SI->getCondition());
- if (SCValue.isUndefined()) {
- SI->setCondition(Constant::getNullValue(SI->getCondition()->getType()));
- BranchesResolved = true;
- visit(SI);
+
+ // Otherwise, it is a branch on a symbolic value which is currently
+ // considered to be undef. Handle this by forcing the input value to the
+ // branch to false.
+ markForcedConstant(BI->getCondition(),
+ ConstantInt::getFalse(TI->getContext()));
+ return true;
+ }
+
+ if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
+ if (SI->getNumSuccessors() < 2) // no cases
+ continue;
+ if (!getValueState(SI->getCondition()).isUndefined())
+ continue;
+
+ // If the input to SCCP is actually switch on undef, fix the undef to
+ // the first constant.
+ if (isa<UndefValue>(SI->getCondition())) {
+ SI->setCondition(SI->getCaseValue(1));
+ markEdgeExecutable(BB, TI->getSuccessor(1));
+ return true;
}
+
+ markForcedConstant(SI->getCondition(), SI->getCaseValue(1));
+ return true;
}
}
- return BranchesResolved;
+
+ return false;
}
namespace {
- Statistic<> NumInstRemoved("sccp", "Number of instructions removed");
- Statistic<> NumDeadBlocks ("sccp", "Number of basic blocks unreachable");
-
//===--------------------------------------------------------------------===//
//
/// SCCP Class - This class uses the SCCPSolver to implement a per-function
- /// Sparse Conditional COnstant Propagator.
+ /// Sparse Conditional Constant Propagator.
///
struct SCCP : public FunctionPass {
+ static char ID; // Pass identification, replacement for typeid
+ SCCP() : FunctionPass(ID) {
+ initializeSCCPPass(*PassRegistry::getPassRegistry());
+ }
+
// runOnFunction - Run the Sparse Conditional Constant Propagation
// algorithm, and return true if the function was modified.
//
bool runOnFunction(Function &F);
-
+
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
}
};
-
- RegisterOpt<SCCP> X("sccp", "Sparse Conditional Constant Propagation");
} // end anonymous namespace
+char SCCP::ID = 0;
+INITIALIZE_PASS(SCCP, "sccp",
+ "Sparse Conditional Constant Propagation", false, false)
-// createSCCPPass - This is the public interface to this file...
+// createSCCPPass - This is the public interface to this file.
FunctionPass *llvm::createSCCPPass() {
return new SCCP();
}
+static void DeleteInstructionInBlock(BasicBlock *BB) {
+ DEBUG(dbgs() << " BasicBlock Dead:" << *BB);
+ ++NumDeadBlocks;
+
+ // Delete the instructions backwards, as it has a reduced likelihood of
+ // having to update as many def-use and use-def chains.
+ while (!isa<TerminatorInst>(BB->begin())) {
+ Instruction *I = --BasicBlock::iterator(BB->getTerminator());
+
+ if (!I->use_empty())
+ I->replaceAllUsesWith(UndefValue::get(I->getType()));
+ BB->getInstList().erase(I);
+ ++NumInstRemoved;
+ }
+}
// runOnFunction() - Run the Sparse Conditional Constant Propagation algorithm,
// and return true if the function was modified.
//
bool SCCP::runOnFunction(Function &F) {
- DEBUG(std::cerr << "SCCP on function '" << F.getName() << "'\n");
- SCCPSolver Solver;
+ DEBUG(dbgs() << "SCCP on function '" << F.getName() << "'\n");
+ SCCPSolver Solver(getAnalysisIfAvailable<TargetData>());
// Mark the first block of the function as being executable.
Solver.MarkBlockExecutable(F.begin());
// Mark all arguments to the function as being overdefined.
- hash_map<Value*, LatticeVal> &Values = Solver.getValueMapping();
- for (Function::aiterator AI = F.abegin(), E = F.aend(); AI != E; ++AI)
- Values[AI].markOverdefined();
+ for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end(); AI != E;++AI)
+ Solver.markAnythingOverdefined(AI);
// Solve for constants.
- bool ResolvedBranches = true;
- while (ResolvedBranches) {
+ bool ResolvedUndefs = true;
+ while (ResolvedUndefs) {
Solver.Solve();
- ResolvedBranches = Solver.ResolveBranchesIn(F);
+ DEBUG(dbgs() << "RESOLVING UNDEFs\n");
+ ResolvedUndefs = Solver.ResolvedUndefsIn(F);
}
bool MadeChanges = false;
// If we decided that there are basic blocks that are dead in this function,
// delete their contents now. Note that we cannot actually delete the blocks,
// as we cannot modify the CFG of the function.
- //
- std::set<BasicBlock*> &ExecutableBBs = Solver.getExecutableBlocks();
- for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
- if (!ExecutableBBs.count(BB)) {
- DEBUG(std::cerr << " BasicBlock Dead:" << *BB);
- ++NumDeadBlocks;
-
- // Delete the instructions backwards, as it has a reduced likelihood of
- // having to update as many def-use and use-def chains.
- std::vector<Instruction*> Insts;
- for (BasicBlock::iterator I = BB->begin(), E = BB->getTerminator();
- I != E; ++I)
- Insts.push_back(I);
- while (!Insts.empty()) {
- Instruction *I = Insts.back();
- Insts.pop_back();
- if (!I->use_empty())
- I->replaceAllUsesWith(UndefValue::get(I->getType()));
- BB->getInstList().erase(I);
- MadeChanges = true;
- ++NumInstRemoved;
- }
- } else {
- // Iterate over all of the instructions in a function, replacing them with
- // constants if we have found them to be of constant values.
- //
- for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
- Instruction *Inst = BI++;
- if (Inst->getType() != Type::VoidTy) {
- LatticeVal &IV = Values[Inst];
- if (IV.isConstant() || IV.isUndefined() &&
- !isa<TerminatorInst>(Inst)) {
- Constant *Const = IV.isConstant()
- ? IV.getConstant() : UndefValue::get(Inst->getType());
- DEBUG(std::cerr << " Constant: " << *Const << " = " << *Inst);
-
- // Replaces all of the uses of a variable with uses of the constant.
- Inst->replaceAllUsesWith(Const);
-
- // Delete the instruction.
- BB->getInstList().erase(Inst);
-
- // Hey, we just changed something!
- MadeChanges = true;
- ++NumInstRemoved;
- }
- }
- }
+
+ for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
+ if (!Solver.isBlockExecutable(BB)) {
+ DeleteInstructionInBlock(BB);
+ MadeChanges = true;
+ continue;
+ }
+
+ // Iterate over all of the instructions in a function, replacing them with
+ // constants if we have found them to be of constant values.
+ //
+ for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
+ Instruction *Inst = BI++;
+ if (Inst->getType()->isVoidTy() || isa<TerminatorInst>(Inst))
+ continue;
+
+ // TODO: Reconstruct structs from their elements.
+ if (Inst->getType()->isStructTy())
+ continue;
+
+ LatticeVal IV = Solver.getLatticeValueFor(Inst);
+ if (IV.isOverdefined())
+ continue;
+
+ Constant *Const = IV.isConstant()
+ ? IV.getConstant() : UndefValue::get(Inst->getType());
+ DEBUG(dbgs() << " Constant: " << *Const << " = " << *Inst);
+
+ // Replaces all of the uses of a variable with uses of the constant.
+ Inst->replaceAllUsesWith(Const);
+
+ // Delete the instruction.
+ Inst->eraseFromParent();
+
+ // Hey, we just changed something!
+ MadeChanges = true;
+ ++NumInstRemoved;
}
+ }
return MadeChanges;
}
namespace {
- Statistic<> IPNumInstRemoved("ipsccp", "Number of instructions removed");
- Statistic<> IPNumDeadBlocks ("ipsccp", "Number of basic blocks unreachable");
- Statistic<> IPNumArgsElimed ("ipsccp",
- "Number of arguments constant propagated");
- Statistic<> IPNumGlobalConst("ipsccp",
- "Number of globals found to be constant");
-
//===--------------------------------------------------------------------===//
//
/// IPSCCP Class - This class implements interprocedural Sparse Conditional
/// Constant Propagation.
///
struct IPSCCP : public ModulePass {
+ static char ID;
+ IPSCCP() : ModulePass(ID) {
+ initializeIPSCCPPass(*PassRegistry::getPassRegistry());
+ }
bool runOnModule(Module &M);
};
-
- RegisterOpt<IPSCCP>
- Y("ipsccp", "Interprocedural Sparse Conditional Constant Propagation");
} // end anonymous namespace
-// createIPSCCPPass - This is the public interface to this file...
+char IPSCCP::ID = 0;
+INITIALIZE_PASS(IPSCCP, "ipsccp",
+ "Interprocedural Sparse Conditional Constant Propagation",
+ false, false)
+
+// createIPSCCPPass - This is the public interface to this file.
ModulePass *llvm::createIPSCCPPass() {
return new IPSCCP();
}
-static bool AddressIsTaken(GlobalValue *GV) {
- for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
- UI != E; ++UI)
- if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
+static bool AddressIsTaken(const GlobalValue *GV) {
+ // Delete any dead constantexpr klingons.
+ GV->removeDeadConstantUsers();
+
+ for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
+ UI != E; ++UI) {
+ const User *U = *UI;
+ if (const StoreInst *SI = dyn_cast<StoreInst>(U)) {
if (SI->getOperand(0) == GV || SI->isVolatile())
return true; // Storing addr of GV.
- } else if (isa<InvokeInst>(*UI) || isa<CallInst>(*UI)) {
+ } else if (isa<InvokeInst>(U) || isa<CallInst>(U)) {
// Make sure we are calling the function, not passing the address.
- CallSite CS = CallSite::get(cast<Instruction>(*UI));
- for (CallSite::arg_iterator AI = CS.arg_begin(),
- E = CS.arg_end(); AI != E; ++AI)
- if (*AI == GV)
- return true;
- } else if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
+ ImmutableCallSite CS(cast<Instruction>(U));
+ if (!CS.isCallee(UI))
+ return true;
+ } else if (const LoadInst *LI = dyn_cast<LoadInst>(U)) {
if (LI->isVolatile())
return true;
+ } else if (isa<BlockAddress>(U)) {
+ // blockaddress doesn't take the address of the function, it takes addr
+ // of label.
} else {
return true;
}
+ }
return false;
}
bool IPSCCP::runOnModule(Module &M) {
- SCCPSolver Solver;
-
+ SCCPSolver Solver(getAnalysisIfAvailable<TargetData>());
+
+ // AddressTakenFunctions - This set keeps track of the address-taken functions
+ // that are in the input. As IPSCCP runs through and simplifies code,
+ // functions that were address taken can end up losing their
+ // address-taken-ness. Because of this, we keep track of their addresses from
+ // the first pass so we can use them for the later simplification pass.
+ SmallPtrSet<Function*, 32> AddressTakenFunctions;
+
// Loop over all functions, marking arguments to those with their addresses
// taken or that are external as overdefined.
//
- hash_map<Value*, LatticeVal> &Values = Solver.getValueMapping();
- for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F)
- if (!F->hasInternalLinkage() || AddressIsTaken(F)) {
- if (!F->isExternal())
- Solver.MarkBlockExecutable(F->begin());
- for (Function::aiterator AI = F->abegin(), E = F->aend(); AI != E; ++AI)
- Values[AI].markOverdefined();
- } else {
+ for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
+ if (F->isDeclaration())
+ continue;
+
+ // If this is a strong or ODR definition of this function, then we can
+ // propagate information about its result into callsites of it.
+ if (!F->mayBeOverridden())
Solver.AddTrackedFunction(F);
+
+ // If this function only has direct calls that we can see, we can track its
+ // arguments and return value aggressively, and can assume it is not called
+ // unless we see evidence to the contrary.
+ if (F->hasLocalLinkage()) {
+ if (AddressIsTaken(F))
+ AddressTakenFunctions.insert(F);
+ else {
+ Solver.AddArgumentTrackedFunction(F);
+ continue;
+ }
}
+ // Assume the function is called.
+ Solver.MarkBlockExecutable(F->begin());
+
+ // Assume nothing about the incoming arguments.
+ for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
+ AI != E; ++AI)
+ Solver.markAnythingOverdefined(AI);
+ }
+
// Loop over global variables. We inform the solver about any internal global
// variables that do not have their 'addresses taken'. If they don't have
// their addresses taken, we can propagate constants through them.
- for (Module::giterator G = M.gbegin(), E = M.gend(); G != E; ++G)
- if (!G->isConstant() && G->hasInternalLinkage() && !AddressIsTaken(G))
+ for (Module::global_iterator G = M.global_begin(), E = M.global_end();
+ G != E; ++G)
+ if (!G->isConstant() && G->hasLocalLinkage() && !AddressIsTaken(G))
Solver.TrackValueOfGlobalVariable(G);
// Solve for constants.
- bool ResolvedBranches = true;
- while (ResolvedBranches) {
+ bool ResolvedUndefs = true;
+ while (ResolvedUndefs) {
Solver.Solve();
- ResolvedBranches = false;
+ DEBUG(dbgs() << "RESOLVING UNDEFS\n");
+ ResolvedUndefs = false;
for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F)
- ResolvedBranches |= Solver.ResolveBranchesIn(*F);
+ ResolvedUndefs |= Solver.ResolvedUndefsIn(*F);
}
bool MadeChanges = false;
// Iterate over all of the instructions in the module, replacing them with
// constants if we have found them to be of constant values.
//
- std::set<BasicBlock*> &ExecutableBBs = Solver.getExecutableBlocks();
+ SmallVector<BasicBlock*, 512> BlocksToErase;
+
for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
- for (Function::aiterator AI = F->abegin(), E = F->aend(); AI != E; ++AI)
- if (!AI->use_empty()) {
- LatticeVal &IV = Values[AI];
- if (IV.isConstant() || IV.isUndefined()) {
- Constant *CST = IV.isConstant() ?
- IV.getConstant() : UndefValue::get(AI->getType());
- DEBUG(std::cerr << "*** Arg " << *AI << " = " << *CST <<"\n");
-
- // Replaces all of the uses of a variable with uses of the
- // constant.
- AI->replaceAllUsesWith(CST);
- ++IPNumArgsElimed;
- }
+ if (Solver.isBlockExecutable(F->begin())) {
+ for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
+ AI != E; ++AI) {
+ if (AI->use_empty() || AI->getType()->isStructTy()) continue;
+
+ // TODO: Could use getStructLatticeValueFor to find out if the entire
+ // result is a constant and replace it entirely if so.
+
+ LatticeVal IV = Solver.getLatticeValueFor(AI);
+ if (IV.isOverdefined()) continue;
+
+ Constant *CST = IV.isConstant() ?
+ IV.getConstant() : UndefValue::get(AI->getType());
+ DEBUG(dbgs() << "*** Arg " << *AI << " = " << *CST <<"\n");
+
+ // Replaces all of the uses of a variable with uses of the
+ // constant.
+ AI->replaceAllUsesWith(CST);
+ ++IPNumArgsElimed;
}
+ }
+
+ for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
+ if (!Solver.isBlockExecutable(BB)) {
+ DeleteInstructionInBlock(BB);
+ MadeChanges = true;
- std::vector<BasicBlock*> BlocksToErase;
- for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
- if (!ExecutableBBs.count(BB)) {
- DEBUG(std::cerr << " BasicBlock Dead:" << *BB);
- ++IPNumDeadBlocks;
- BlocksToErase.push_back(BB);
-
- // Delete the instructions backwards, as it has a reduced likelihood of
- // having to update as many def-use and use-def chains.
- std::vector<Instruction*> Insts;
TerminatorInst *TI = BB->getTerminator();
- for (BasicBlock::iterator I = BB->begin(), E = TI; I != E; ++I)
- Insts.push_back(I);
-
- while (!Insts.empty()) {
- Instruction *I = Insts.back();
- Insts.pop_back();
- if (!I->use_empty())
- I->replaceAllUsesWith(UndefValue::get(I->getType()));
- BB->getInstList().erase(I);
- MadeChanges = true;
- ++IPNumInstRemoved;
- }
-
for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) {
BasicBlock *Succ = TI->getSuccessor(i);
- if (Succ->begin() != Succ->end() && isa<PHINode>(Succ->begin()))
+ if (!Succ->empty() && isa<PHINode>(Succ->begin()))
TI->getSuccessor(i)->removePredecessor(BB);
}
if (!TI->use_empty())
TI->replaceAllUsesWith(UndefValue::get(TI->getType()));
- BB->getInstList().erase(TI);
+ TI->eraseFromParent();
- } else {
- for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
- Instruction *Inst = BI++;
- if (Inst->getType() != Type::VoidTy) {
- LatticeVal &IV = Values[Inst];
- if (IV.isConstant() || IV.isUndefined() &&
- !isa<TerminatorInst>(Inst)) {
- Constant *Const = IV.isConstant()
- ? IV.getConstant() : UndefValue::get(Inst->getType());
- DEBUG(std::cerr << " Constant: " << *Const << " = " << *Inst);
-
- // Replaces all of the uses of a variable with uses of the
- // constant.
- Inst->replaceAllUsesWith(Const);
-
- // Delete the instruction.
- if (!isa<TerminatorInst>(Inst) && !isa<CallInst>(Inst))
- BB->getInstList().erase(Inst);
-
- // Hey, we just changed something!
- MadeChanges = true;
- ++IPNumInstRemoved;
- }
- }
- }
+ if (&*BB != &F->front())
+ BlocksToErase.push_back(BB);
+ else
+ new UnreachableInst(M.getContext(), BB);
+ continue;
+ }
+
+ for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
+ Instruction *Inst = BI++;
+ if (Inst->getType()->isVoidTy() || Inst->getType()->isStructTy())
+ continue;
+
+ // TODO: Could use getStructLatticeValueFor to find out if the entire
+ // result is a constant and replace it entirely if so.
+
+ LatticeVal IV = Solver.getLatticeValueFor(Inst);
+ if (IV.isOverdefined())
+ continue;
+
+ Constant *Const = IV.isConstant()
+ ? IV.getConstant() : UndefValue::get(Inst->getType());
+ DEBUG(dbgs() << " Constant: " << *Const << " = " << *Inst);
+
+ // Replaces all of the uses of a variable with uses of the
+ // constant.
+ Inst->replaceAllUsesWith(Const);
+
+ // Delete the instruction.
+ if (!isa<CallInst>(Inst) && !isa<TerminatorInst>(Inst))
+ Inst->eraseFromParent();
+
+ // Hey, we just changed something!
+ MadeChanges = true;
+ ++IPNumInstRemoved;
}
+ }
// Now that all instructions in the function are constant folded, erase dead
// blocks, because we can now use ConstantFoldTerminator to get rid of
for (unsigned i = 0, e = BlocksToErase.size(); i != e; ++i) {
// If there are any PHI nodes in this successor, drop entries for BB now.
BasicBlock *DeadBB = BlocksToErase[i];
- while (!DeadBB->use_empty()) {
- Instruction *I = cast<Instruction>(DeadBB->use_back());
+ for (Value::use_iterator UI = DeadBB->use_begin(), UE = DeadBB->use_end();
+ UI != UE; ) {
+ // Grab the user and then increment the iterator early, as the user
+ // will be deleted. Step past all adjacent uses from the same user.
+ Instruction *I = dyn_cast<Instruction>(*UI);
+ do { ++UI; } while (UI != UE && *UI == I);
+
+ // Ignore blockaddress users; BasicBlock's dtor will handle them.
+ if (!I) continue;
+
bool Folded = ConstantFoldTerminator(I->getParent());
- assert(Folded && "Didn't fold away reference to block!");
+ if (!Folded) {
+ // The constant folder may not have been able to fold the terminator
+ // if this is a branch or switch on undef. Fold it manually as a
+ // branch to the first successor.
+#ifndef NDEBUG
+ if (BranchInst *BI = dyn_cast<BranchInst>(I)) {
+ assert(BI->isConditional() && isa<UndefValue>(BI->getCondition()) &&
+ "Branch should be foldable!");
+ } else if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
+ assert(isa<UndefValue>(SI->getCondition()) && "Switch should fold");
+ } else {
+ llvm_unreachable("Didn't fold away reference to block!");
+ }
+#endif
+
+ // Make this an uncond branch to the first successor.
+ TerminatorInst *TI = I->getParent()->getTerminator();
+ BranchInst::Create(TI->getSuccessor(0), TI);
+
+ // Remove entries in successor phi nodes to remove edges.
+ for (unsigned i = 1, e = TI->getNumSuccessors(); i != e; ++i)
+ TI->getSuccessor(i)->removePredecessor(TI->getParent());
+
+ // Remove the old terminator.
+ TI->eraseFromParent();
+ }
}
-
+
// Finally, delete the basic block.
F->getBasicBlockList().erase(DeadBB);
}
+ BlocksToErase.clear();
}
// If we inferred constant or undef return values for a function, we replaced
// all call uses with the inferred value. This means we don't need to bother
// actually returning anything from the function. Replace all return
// instructions with return undef.
- const hash_map<Function*, LatticeVal> &RV =Solver.getTrackedFunctionRetVals();
- for (hash_map<Function*, LatticeVal>::const_iterator I = RV.begin(),
- E = RV.end(); I != E; ++I)
- if (!I->second.isOverdefined() &&
- I->first->getReturnType() != Type::VoidTy) {
- Function *F = I->first;
- for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
- if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()))
- if (!isa<UndefValue>(RI->getOperand(0)))
- RI->setOperand(0, UndefValue::get(F->getReturnType()));
- }
+ //
+ // Do this in two stages: first identify the functions we should process, then
+ // actually zap their returns. This is important because we can only do this
+ // if the address of the function isn't taken. In cases where a return is the
+ // last use of a function, the order of processing functions would affect
+ // whether other functions are optimizable.
+ SmallVector<ReturnInst*, 8> ReturnsToZap;
+
+ // TODO: Process multiple value ret instructions also.
+ const DenseMap<Function*, LatticeVal> &RV = Solver.getTrackedRetVals();
+ for (DenseMap<Function*, LatticeVal>::const_iterator I = RV.begin(),
+ E = RV.end(); I != E; ++I) {
+ Function *F = I->first;
+ if (I->second.isOverdefined() || F->getReturnType()->isVoidTy())
+ continue;
+
+ // We can only do this if we know that nothing else can call the function.
+ if (!F->hasLocalLinkage() || AddressTakenFunctions.count(F))
+ continue;
+
+ for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
+ if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator()))
+ if (!isa<UndefValue>(RI->getOperand(0)))
+ ReturnsToZap.push_back(RI);
+ }
+ // Zap all returns which we've identified as zap to change.
+ for (unsigned i = 0, e = ReturnsToZap.size(); i != e; ++i) {
+ Function *F = ReturnsToZap[i]->getParent()->getParent();
+ ReturnsToZap[i]->setOperand(0, UndefValue::get(F->getReturnType()));
+ }
+
// If we infered constant or undef values for globals variables, we can delete
// the global and any stores that remain to it.
- const hash_map<GlobalVariable*, LatticeVal> &TG = Solver.getTrackedGlobals();
- for (hash_map<GlobalVariable*, LatticeVal>::const_iterator I = TG.begin(),
+ const DenseMap<GlobalVariable*, LatticeVal> &TG = Solver.getTrackedGlobals();
+ for (DenseMap<GlobalVariable*, LatticeVal>::const_iterator I = TG.begin(),
E = TG.end(); I != E; ++I) {
GlobalVariable *GV = I->first;
assert(!I->second.isOverdefined() &&
"Overdefined values should have been taken out of the map!");
- DEBUG(std::cerr << "Found that GV '" << GV->getName()<< "' is constant!\n");
+ DEBUG(dbgs() << "Found that GV '" << GV->getName() << "' is constant!\n");
while (!GV->use_empty()) {
StoreInst *SI = cast<StoreInst>(GV->use_back());
SI->eraseFromParent();
}
M.getGlobalList().erase(GV);
+ ++IPNumGlobalConst;
}
-
+
return MadeChanges;
}